What are some historical analogies to Susan Collins’ surprise win?

[Matty]

What are some other examples in relatively recent memory of a sitting senator defying expectations and winning a state despite horrible pre election polling and the state voting for opposite party for prez election?

[Left Wing]

It's kind of like WI-SEN 2016 minus the state voting for the opposite party part.

[○∙◄☻¥tπ[╪AV┼cVê└]

Not sitting but I think ND 2012.

[Left Wing]

Not sitting but I think ND 2012.

Heitkamp wasn't polling that bad. It was pretty much a dead heat.

[SenatorCouzens]

I think it's hard to find a parallel because long serving battle tested incumbents who won their last three Senate races in land slides have, historically speaking, seldom been considered Dead on Arrival by the chattering class the way Susan Collins was.

That's what makes this race so unique. She was sort of written off despite her previous strength.

[Tekken_Guy]

FL-SEN 2018 and WI-SEN 2016. All senate races people thought Democrats had in the bag. I can’t think of anyone who expected the GOP to come out on top.

[DaleCooper]

I don't know but I do remember getting some snark when I said a couple months ago that I sensed Collins was turning things around in the ME Senate campaign so I can at least take solace in being a bit vindicated.

To answer the question, maybe Tester in 2012? He wasn't a longtime incumbent, though.

[MT Treasurer]

The margin of victory was more surprising than the actual victory in this race.  

2008

RCP average: Collins +14.6
Actual result: Collins +23

https://www.realclearpolitics.com/epolls/2008/senate/me/maine_senate-564.html

2014

RCP average: Collins +29.2
Actual result: Collins +37

https://www.realclearpolitics.com/epolls/2014/senate/me/maine_senate_collins_vs_bellows-4168.html

Gideon was only ahead in the RCP average by 4.5-5 points this year, so she could not afford a similar Collins overperformance. There were a lot of warning signs people just overlooked or wanted to overlook: (a) Collins' own history of outperforming the polling averages, (b) the recent history of polling overstating Democratic strength in this particular state, (c) Gideon's consistent underperformance of Biden's numbers in the polls, and (d) the ‘Trump rubber stamp’ attacks having the unintended effect of removing enough Trump supporters'/Republicans' doubts about Collins and therefore increasing the likelhood of Collins receiving an outright majority even before IRV.

[Penn_Quaker_Girl]

FL-SEN 2018 and WI-SEN 2016. All senate races people thought Democrats had in the bag. I can’t think of anyone who expected the GOP to come out on top.

I actually did have Collins winning this race through Election Day, BUT it was probably due more in part to me not paying close enough attention to it and just assuming Susan Collins would still be Susan Collins (as opposed to some bold going-against-the-grain call). 

[Pollster]

 

2008

RCP average: Collins +14.6
Actual result: Collins +23

https://www.realclearpolitics.com/epolls/2008/senate/me/maine_senate-564.html

2014

RCP average: Collins +29.2
Actual result: Collins +37

https://www.realclearpolitics.com/epolls/2014/senate/me/maine_senate_collins_vs_bellows-4168.html

In both races, the Democrat performed almost exactly at their average and Collins wound up consolidating the undecided/uncommitted voters (probably Dem-leaners who didn't want to commit to voting Republican but were always more likely than not with Collins).

It looks like Gideon's polling suffered from both that Collins consolidation phenomenon, as well as pollsters generally modeling for a 2018-style environment, which likely made her average vote share a bit too high. If we assume that Gideon's average was a few points too high throughout the race, then the same "Dem hitting their average/Collins consolidating" pattern probably holds in this race as well. The fact that Collins' overperformance was roughly the same 8 points both times, and her final average (probably lowballed for the same reason Gideon's was overshot) this year was around 42% before she won with 51%, fits into this scenario almost perfectly.

A good (though obviously imperfect) historical comparison is NV-Sen 2010: incumbent is a multi-term institution with long history of consolidating in the end, polls modeling a different turnout than actually happened, giving the incumbent a lower share and the challenger a higher share than was the truth.

[Vosem]

What are some other examples in relatively recent memory of a sitting senator defying expectations and winning a state despite horrible pre election polling and the state voting for opposite party for prez election?

It's by no means a complete analogy (since what I'm thinking of happened in a friendly state), but a beloved long-time Senator being left for dead in polls and then over-performing them by double digits happened in AK-Sen 2008 (though Alaska voted Republican up-ballot and Stevens still narrowly lost; he just came within 1% of winning instead of being blown out by 20 points like polling suggested).

[MATTROSE94]

New Hampshire Senate 1996.

[Figueira]

It wasn't really that surprising; the polls were moving in Collins's direction leading up to Election Day. WI 2016 is a pretty good analogy actually, although obviously the dynamics were very different.