Right now, Iowa has 612,112 registered Republicans.
If the turnout is at the usual 20 percent or so, that would mean about 122,000 Republicans will turn out Monday night. Some GOP consultants are predicting turnout could be significantly higher, perhaps 140,000 – bumping up turnout to about 22 percent.
Right now, Iowa has 584,111 registered Democrats. That party enjoyed much higher caucus turnout in 2008 (with the high profile Obama vs. Clinton vs. Edwards battle) with 39.5 percent; their turnout in 2004 (Kerry, Dean, Gephardt) was 23 percent. If turnout is at the 2004 level, we should see about 135,000 Democrats on caucus night; if it’s at 2008 level, we should see 230,000 Democrats at the caucuses.
In other words, the maximum turnout we should expect in both caucuses combined is about 370,000.
The CBS News Battleground Tracker poll asked 1,247 registered voters, “How likely is it that you will vote in the 2016 Presidential caucus in Iowa?” and 52 percent said they “definitely would vote.”
Either turnout will be unlike anything we’ve ever seen before – a half-million voters – or a significant chunk of those people who are telling CBS they’re definitely participating aren’t going to participate.
CNN called 2002 adult Iowans and found 266 likely to participate in the GOP caucus and 280 likely to participate in the Democratic one. At first glance, that seems like a nice, tight voter screen, but that still adds up to 546 respondents out of 2002 – 27 percent. And remember that’s not 2002 registered members of either party; that’s of any adult Iowan who answered the phone. Iowa has 2.37 million people above age 18. If 27 percent of all 2.37 million adults in Iowa participate in the caucuses, that would be a turnout of almost 640,000 people.
Look, determining who’s actually going to show up on caucus night is difficult. Maybe Trump and Cruz will drive up turnout in the GOP caucus, and maybe Sanders will reenact some of Obama’s magic. We’re not going to know who actually participates until well into the evening on February 1.
But if the final results look significantly different than these last couple polls, it will be fair to ask if the polls counted a bunch of “likely caucusgoers” who were not, in fact, all that likely.