How Reliable Are the Iowa Caucus Polls on June 10th? MoJo Investigates.

Over on Twitter, someone suggested taking a look at early polls of the Iowa caucuses from past years to see how they panned out. On the Democratic side, it’s a little tricky because there were really only two candidates in 2016 and one of them was the clear frontrunner. That’s not much of a comparison to this year, so I went back to 2008:
Support for John Edwards (remember him?) and Hillary Clinton stayed pretty steady during the entire campaign, while 3rd-place candidate Barack Obama quietly scooped up nearly all of the undecided vote and ended up winning by a wide margin.
On the Republican side, 2016 featured a huge number of candidates, which makes it a pretty good comparison for Democrats this year. Here are the top ten candidates on June 10 before the caucus date:
This is even better news for today’s also-rans. The early leader, Scott Walker, wasn’t even in the race by the time the caucuses were held, while seventh-place Ted Cruz won and tenth-place Donald Trump came in a close second.
I think the only real lesson you can take away from this is that you’re in trouble if you aren’t even managing, say, 5 percent support right now.¹ For what it’s worth, RCP has only five candidates currently polling above that level:

Joe Biden (23.8%)
Bernie Sanders (18.8%)
Pete Buttigieg (12%)
Elizabeth Warren (9.3%)
Kamala Harris (7.5%)

This looks . . . about right to me. Maybe add Cory Booker and Amy Klobuchar as dark horses, and I think that’s pretty much the field.
¹As usual, Donald Trump is a huge outlier.