There were 2 PR candidates which were elected on the YP PR slate in 2010 but were defeated for re-election in 2016 which due to their election experience being illustrative on strategies of getting elected on the PR slate I was tracking this election. Both got elected. Looking at the election history of these two MPs elected on the PR slate helps to explain some political strategies around being elected on the PR slate.
Just to get details out of the way, the PR slate is based on an party open list process where a voter can vote for a party OR a PR list candidate which gets accrued to the party to calculate the PR seats allocated to said party. The candidates on the list that are elected are based on the number of votes each member on the list gets.
So the correct strategy of a PR list candidate is to
a) Make sure there is a large enough personal vote so people vote for your name
b) Be on a party list that can actually win enough votes to have any PR seats elected to allocate
c) Make sure other PR candidates on the party list you are on have a smaller personal vote than you do.
From a political party's point of view you want to get candidates on your list that have a large personal vote to augment your own party loyalists that will vote for the party itself so you expand the number of votes accrued to your party.
The first candidate go over the election history of is
山田太郎(Tarō Yamada).
He has a business background but got into politics given his libertarian positions and ran as a PR candidate for YP in 2010. He got 30.6K votes which placed him 10th. But YP won enough votes for 7 seat in 2010 so he was not elected. In 2012 several YP MPs elected on the 2010 PR slate choose to resign to run in the 2012 Lower House elections on the YP or JRP ticket. So as a result 山田太郎(Tarō Yamada) which was next in line was put into the Upper House in late 2012.
YP dissolved in 2014 so 山田太郎(Tarō Yamada) joined YP successor AEJ which mostly dissolved before the 2016 Upper House elections. 山田太郎(Tarō Yamada) in the meantime re-invited himself politically and became an advocate of Otaku or Japanese male youth which are fans of Anime and manga. He fought against laws to regulate hentai due to linkages to child pornography. He became a hero of what is called the "geek vote" of young males that are really into Hentai. With this base of support he sought to run on the ORA PR list in 2016. Other ORA PR candidates pushed backed on accepting 山田太郎(Tarō Yamada) into the ORA PR list seeing him as unfairly denying them their rightful place as the winners on the ORA list. ORA high command backed down and did not add 山田太郎(Tarō Yamada) on the ORA PR list.
山田太郎(Tarō Yamada) in 2016 ran on Third Pole and LDP Libertarian splinter NPR instead. He ended up winning a surprising 291K votes. But NRP even with the 291K votes won around 580K votes on the PR list which is only 1.04% of the PR vote and not enough for it to win a seat which would have gone to 山田太郎(Tarō Yamada). So while 山田太郎(Tarō Yamada) has as large personal vote he did not run for a party that had enough support for him to win a seat. ORA of course made a mistake here. 山田太郎(Tarō Yamada)'s 291K was by itself 0.52% of the national PR vote which had he ran for ORA would have for sure given ORA an extra PR seat to allocate and not hurt other ORA PR candidates to win a seat due to them.
山田太郎(Tarō Yamada)'s large PR vote in 2016 caught LDP's eye. Under the rule "If you win you are LDP", LDP courted 山田太郎(Tarō Yamada) who quickly jump on board and joined LDP to run for LDP in 2019. The LDP figures if 山田太郎(Tarō Yamada) and bring his 291K with him then all that vote would count toward LDP's vote share. As it is 山田太郎(Tarō Yamada) win a massive 540K votes which by itself was 1.08% of the entire PR vote and put him to be second on the LDP PR list and is duly elected. 山田太郎(Tarō Yamada) running for LDP was a win-win. He ran for a party which had prospect of winning a bunch of seats and given his vote base he should be able to come in the top 19 (the 19th LDP PR winner won 132K votes) giving him a win unlike 2016 where 291K did not yield him a seat. For LDP they get an extra 0.5%-1.0% vote share to LDP that could have gone to another party had 山田太郎(Tarō Yamada) ran for another party.
The second candidate is also interesting. He is
柴田巧(Takumi Shibata).
He was a LDP local politician in 富山(Toyama) and was elected to several terms in the prefecture assembly and has deep roots in the prefecture. In 2009 Lower House election he sought the LDP nomination to run in the LDP stronghold of 富山(Toyama) 3rd district which became an open seat. He was denied and instead ran as a LDP rebel. The result was
LDP 45.9%
IND(DPJ) 36.0%
Takumi 17.3% (around 51K votes)
After his defeat 柴田巧(Takumi Shibata) joined the rising YP and ran as a YP PR candidate in the 2010 Upper House elections. He won around 88K overall of which 62K was from 富山(Toyama) which actually placed him first in the YP list since the other YP PR candidate did not really have a large personal vote. To show the size of 柴田巧(Takumi Shibata)'s personal vote in 富山(Toyama), YP won 20.3% of the PR vote in 富山(Toyama) in 2010. 柴田巧(Takumi Shibata) by himself won 11.0% of the PR vote for 富山(Toyama) which means he pretty much carried half the YP PR vote in 富山(Toyama). In 2012 Lower House elections without 柴田巧(Takumi Shibata)'s name YP only won 6.7% of the PR vote in 富山(Toyama).
After YP split in 2014 柴田巧(Takumi Shibata) went with YP splinter UP and which merged into JIP. In early 2016 after ORA split from JIP, JIP merged with DPJ to form DP. So for the 2016 Upper House elections 柴田巧(Takumi Shibata) ran on the DP PR list. 柴田巧(Takumi Shibata) actually won 73K votes (50K votes of it from 富山(Toyama) which means if anything his personal vote in 富山(Toyama) grew from 2010) But 73K placed him 17th on the DP list as the DP PR list had many PR candidates with large personal vote. As it is DP only won enough votes for 11 seats so 柴田巧(Takumi Shibata) was not elected. 柴田巧(Takumi Shibata) did make a huge impact on 富山(Toyama). DP won 24.2% of the PR vote in 富山(Toyama) of which 柴田巧(Takumi Shibata) 's personal vote was 10.5% of it. Back in 2014 DPJ won 10.3% of the 富山(Toyama) PR vote and an undivided JIP (ORA had not split out yet) won 16.9% of the vote. It is clear DP getting 柴田巧(Takumi Shibata) to run for it gained it a bunch of PR votes in 富山(Toyama) even though 柴田巧(Takumi Shibata) failed to win.
柴田巧(Takumi Shibata) stayed in DP and went to join HP in 2017 when DP was de facto dissolved. He again ran in 富山(Toyama) 3rd district as the HP candidate against his old LDP rival of 2009. He was defeated
LDP 63.9%
HP 28.2% (around 62K)
JCP 8.0%
For 2019 Upper House elections 柴田巧(Takumi Shibata) was recruited by JRP given his personal vote in 富山(Toyama) to run for JRP PR slate. He won around 54K votes which placed him 4th place on the JRP list. This is because other than NPD founder and leader 鈴木宗男(Suzuki Muneo) JRP's PR list did not have that many candidates that has a large personal vote. As a result 柴田巧(Takumi Shibata) was elected even though his 54K votes was less than the 73K votes he won in 2016 on the DP PR list. As it is he won only 33K votes in 富山(Toyama) which is less than 2010 and 2016 but still carried JRP in 富山(Toyama). As it is JRP won 14.5% of the PR vote in 富山(Toyama) of which 8.3% of it was won by 柴田巧(Takumi Shibata). In 2017 Lower House election without 柴田巧(Takumi Shibata) name on the JRP list JRP won 7.0% of the PR vote. So it is clear that 柴田巧(Takumi Shibata) had carried JRP in 富山(Toyama) in 2019.
The main lessons of these two candidates is that a large personal vote, even if concentrated in a prefecture, is not enough to win FPTP seats but can help you win on the PR slate as long as you join the right party list that can win seats but do not have too many heavy personal vote candidates on the same party list to take slots from you.
I wrote about 柴田 巧 (Shibata Takumi) back in 2016
Looking through the PR vote section by prefecture also resolved another mysterious result which I could not explain before. Telling the tale of my discovery also helps tell a bigger story of why LDP win.
The initial mystery was around the result in the 1- district and old LDP stronghold 富山(Toyama). What took place was was turnout surged from 2013 by 5.4% when the rest of Japan turnout went up by around 2%. Then on the PR section the DP PR vote surged to 24.22% from 10.3% in 2014 and 9.41% in 2013. As a result LDP+KP PR vote was at 54% which was a drop of 2.3% from 2014 when LDP+KP PR went up by 2.6% in the PR section since 2014 across Japan. The in the district section for Toyama LDP completely overperformed its PR vote over the united opposition candidate. Based on my regression model, which uses PR vote section and looks at incumbency effects, the LDP got over 8.4% vote share over what my model would imply. Part of it can be explained by a popular LDP incumbant and weak opposition independent candidate but then would would there be a surge of DP PR vote with high turnout only for the same voters to then just vote LDP on the district vote.
This mystery got unraveled when I looked at the PR section by candidate and prefecture. It turned out that an incumbant ex-YP MP 柴田 巧 (Shibata Takumi) who won in 2010 on the YP PR slate but then joined DP won a large amount of the PR vote in his home prefecture of Toyama. Out of the 116.5K PR votes cast for DP in Toyama, 柴田 巧 (Shibata Takumi) himself won as a vote for him 50.3K. So nearly half of the DP PR vote in Toyama was cast for Shibata. Just for comparison, in other prefectures the DP PR vote is usually around 20% for candidate names (let alone just one candidate) and 80% for the party itself. Shibata lost reelection because even though he won 50.3K in Toyama he won only 73K over all of Japan which placed him 17th on the DP PR list and DP only won enough votes to win 11 seats.
柴田 巧 (Shibata Takumi)
Looking at 柴田 巧 (Shibata Takumi) himself. He was with the LDP in the Toyama prefecture assembly but in 2009 ran as a LDP rebel in the Lower House elections and lost but winning 50K votes in 1 of the 3 Toyama Lower House districts. Then he joined YP and ran on the PR list for YP in 2010. In 2010 Shibata won 87.8K vote of which most of it must have come from Toyama which place him first in the YP PR list of which 4 was elected based on a 8.9% vote share and over 4.7 million votes. 2010 YP PR list did not have that many well known candidates and 90% of the PR vote for the YP party itself so 87.8K was enough to place him first. 2016 DP PR list had a lot more well known candidates so a slight decrease in total number of votes for Shibata drove him to 17th place. So Shibata went from a big fish in a small pond to a small fish in a big pond and lost re-election. It seems most of Shibata's votes in Toyama are his personal vote and would otherwise vote LDP. Just to give an idea the impact Shibata has on the PR vote, in 2010 when Shibata ran on the YP PR slate, YP won 20.34% of the Toyama PR vote. In 2012 and 2014 when YP did not have Shibata as a personal candidate on the PR list (of course 2012 was a Lower House election where one cannot for a PR candidate anyway) YP won 6.67% and 4.96% in the PR section of Toyama.
So now the mystery is solved. The DP surge in Toyama 2016 was based on the fact that 柴田 巧 (Shibata Takumi) by himself won over 10% of the PR vote which pushed to the DP PR vote share to above 24% when it recently had been in the single digits. But most of this vote are the personal vote of Shibata and when left to vote on the district section mostly voted LDP. It seems given the size of Shibata's personal vote it is likely he will run in the next Lower House elections so he can add his personal vote with the center-left and possibly JCP and make his race potentially competitive.
The story of 柴田 巧 (Shibata Takumi) is very instructive on why LDP wins. For each 柴田 巧 (Shibata Takumi) who is a LDP rebel, many other local politicians with personal votes stay in LDP. The dynamic is the following:
LDP is in charge of central government -> Local governments cannot issue debt -> Center Government distributes subsidies to local government via the MPs and MLAs of said prefecture -> local politicians join LDP so bring home the bacon -> local politician personal votes transferred to LDP for national elections -> LDP in charge of central government.
At least for now Shibata being part of DP has not lead to his personal base going over to DP as seen by the district vote but over time that could change.
I also wrote about 山田太郎(Tarō Yamada) in 2016 as well
Another set of data I was able to dig out of the PR vote distribution by candidate was able to explain the unexpectedly large PR vote share by NPR (1.04%) as well as a tale of how ORA threw away a PR seat.
NPR is pretty much a defunct Right Libertarian LDP splinter party. Without knowing too much at the ground I figured they were only good for 0.5%. but they actually managed 1.04% which was still not enough to win a PR seat but still higher than I expected. I looked into why. It turns out an ex-YP incumbent MP 山田太郎 (Yamada Taro) won single handedly over 290K votes which itself was 0.52% of total PR vote share making him the 13th largest vote getter of all the PR candidates running. So NPR got around 0.5% of the PR vote but when added by Yamada's vote put NPR past 1% vote share. Of course since NPR failed to win a seat on PR Yamada was not elected.
山田太郎 (Yamada Taro)
山田太郎 (Yamada Taro) was elected as part of the class of 2010 YP slate. When YP became defunct at the end of 2014 he joined AEJ. While there he took on the cause of freedom of speech when it came to laws that try to regulate Hentai comics books on the premise of stopping child pornargraphy. This appears to have won him the support of a Hentai reading male youth voting bloc the media call the Geek Vote. In early 2016 Yamada quite AEJ when it was clear AEJ will not even try to contest in 2016 and joined ORA who nominated him to be their candidate for 埼玉(Saitama). Yamada quit ORA claiming that he joined the the premise he would be put in the ORA PR list a fact ORA disputed. From Yamada's point of view running in Saitama would lead to sure defeat when his support is evenly spread across Japan which is a perfect match for a PR candidate. ORA's concern is that having Yamada on its PR list would only cannibalize the ORA PR vote and offend other ORA PR list candidate who would see Yamada potentially large vote as squeezing them out of their sure seat. So Yamada ran on NPR PR list winning a large number of votes from the "Geek voting bloc" but failing re-election. ORA made a big mistake as Yamada's ability to win over 0.5% of the national PR vote shows that he as independent draw and had he run on the ORA PR would have easily added a seat, won by Yamada, to the ORA seat count at the expense of LDP.