Reality check:Since '96, 3rd place candidate has only won >2 primary states once

[Mr. Morden]

Something to keep in mind here re: primary predictions: In the past 25 years, we’ve had 9 different presidential primary contests without an incumbent president.  Here’s the track record for the guy who came in 3rd place in each of them:

1996 GOP: Forbes won Arizona and Delaware.
2000 Dems: There were really only two candidates, so there was no 3rd place.
2000 GOP: Keyes won zero states.
2004 Dems: Dean won his home state of Vermont.
2008 Dems: Edwards won zero states.
2008 GOP: Huckabee won seven states.
2012 GOP: Gingrich won Georgia and South Carolina.
2016 Dems: O’Malley won zero states.
2016 GOP: Whether you count Kasich or Rubio as third place, it doesn’t matter.  They both only won one state each.  (Though Rubio did win DC and Puerto Rico, in addition to Minnesota.  But DC and Puerto Rico aren't states.)

So out of those past nine races, Huckabee in 2008 is the only time that the third place guy managed to win more than two states.  Every other time, the top two candidates ended up winning more than 45 states between them.  This includes cases like the GOP races in 2012 and 2016, where you had a big field of candidates, and many folks during the invisible primary period were saying “OMG!  The field is huge, and the map is going to end up like a checkerboard because there will be no consensus among the voters!”

So keep that in mind when you make your 2020 primary predictions.  The fact that the field is big, and there isn’t a consensus frontrunner right now, doesn’t mean that it’s not going to rapidly coalesce into a race with no more than two main frontrunners once the voting gets underway.

*However*, that does *not* mean that a contested convention is out of the question.  It’s just that it wouldn’t happen the way many here seem to think.  A contested convention could happen if you have something like the 2016 GOP race, but using the Democrats’ proportional delegate allocation rules: You have two frontrunners (in the 2016 case, Trump and Cruz) who between them win virtually every state, but neither of them is getting a majority of the vote anywhere because you also have one or two 3rd place candidates (Kasich and Rubio) sticking around in the race, and continuing to get double digit support.  With the Dem. delegate rules, that would get you a contested convention, even with virtually every state being won by one of two people.

But the kicker is that that 3rd (and 4th?) place candidate would have to stick it out, and not formally drop out of the race and release their delegates.  If they release their delegates, then those delegates would probably just drift over to the frontrunner, and prevent a contested convention from happening.  So you really need a big split in the party for a contested convention to happen.  You need a scenario where the likely nominee is someone who some committed faction of the party with a non-negligible %age of delegates is refusing to support.

[Mr. Morden]

2008 GOP: Huckabee won seven states.

Some would consider Romney as the 3rd place candidate.

Well, Romney got more votes than Huckabee, plus he had more delegates at the time that he dropped out.  Huckabee just barely caught up to Romney in delegates only because he stayed in the race for several weeks past the point at which it was obvious that McCain had the nomination effectively wrapped up, even if he hadn't quite mathematically clinched it.

[Mr. Morden]

Argument to be made if Trump hadn't run, we would've likely seen a contested convention on the GOP side. Romney had the right balance of appeal to moderate/liberal republicans and conservatives. With Christie damaged by his baggage, it would be up to Jeb and if he failed to get the job done, it might've lead to fractured field, where not one candidate had the right balance to cultivate a broad cross-section of voters.

The Republican delegate allocation rules make it harder for a contested convention to happen than the Dem. rules do.  But anyway, like I said upthread, the big issue even in a highly divided field is whether the 3rd and 4th place candidates are willing to accept defeat.

If you're a distant 3rd place, and have no realistic chance of becoming the presidential nominee even at a contested convention, do you concede defeat and formally withdraw from the race and release your delegates?  If you release your delegates, then presumably the guy who's in 1st place will be able to pick off enough of them to get a majority, and there is no contested convention.  (I think that's what happened for the Dems in '84 and '88?  Is that right?  I don't think either Mondale '84 or Dukakis '88 had a delegate majority just from the primary results alone, but had to rely on delegates from other candidates who'd dropped out?  But I was too young to be paying attention back then, so someone correct me if I'm wrong.  )  Or do you stick it out and force a contested convention, in the hope of being a power player at said convention, possibly hoping to become a compromise choice yourself?

In 2016, because the GOP frontrunner was Trump, and the other candidates all hated him, you could have had a contested convention scenario if there'd been slightly different delegate allocation rules, because Cruz and Kasich both thought Trump was an unacceptable nominee, and so they were reluctant to drop out of the race and let him win (up until the point at which it was clear that he was going to win anyway).  So the question for Dems in 2020 is whether it's possible that the split within the party will grow so large that the 2nd/3rd/4th place candidates are actually willing to force a contested convention in order to stop whoever the frontrunner is.