Future of the anti-Trump GOP voters

[Mr. Morden]

Exit polls from 2012 and 2016:

https://www.cnn.com/election/2012/results/race/president/
https://www.cnn.com/election/2016/results/exit-polls

The Republican vote in 2012:
Romney 93%
Obama 6%
3rd Party 1%

The Republican vote in 2016:
Trump 88%
Clinton 8%
3rd Party 4%

[Of course, this doesn't count those Republicans who skipped the election altogether.  This is just among those who voted.]

Are the 12% of self-identified Republicans who didn't vote for Trump in 2016 a very different group of voters than the 7% who didn't vote for Romney in 2012?  Or is there heavy overlap?  Are there always just a bunch of people in the party (in both parties really) who spend many elections in a row not voting for their party's nominee for president, yet holding on to the party identification for some reason (maybe for more local races)?  Or is there something especially different about those Republicans who didn't vote Trump in 2016?

[Mr. Morden]

Again, like I said on the last page, the exit polls say that, among Republicans who voted for prez in 2016 (so this omits the #NeverTrumpers who were non-voters), 12% voted for someone other than Trump.  But the exit polls also say that 7% of Republicans voted for someone other than Romney in 2012.  So I'm still wondering if it's just the case that there are a bunch of chronic party switchers, self-described Republicans who always vote Dem. at the presidential level, and then vice versa as well?  Or maybe there are just always people who are in the middle of transitioning from one party the other?  (So, Clinton voting Republicans in 2016 are on their way to becoming Dems, but before that, there were Obama voting Republicans in 2012 on their way to becoming Dems, but the former group was just a bit bigger.)

In other words, is there actually something fundamentally different about the non-Trump supporting Republicans from 2016, or do we see such a group in every election, but it was just somewhat bigger than normal that time?