© Andrew Harnik/AP Caucus goers check in before Democratic presidential candidate Sen. Elizabeth Warren, D-Mass., speaks at a caucus at Roosevelt Hight School, Monday, Feb. 3, 2020, in Des Moines, Iowa.

There's still a lot we don't know about the 2020 Iowa Democratic caucuses, including who won the contest.

But we do have an early indication about turnout. The Iowa Democratic Party said Monday night that early data showed it looked to be on pace with 2016, when 172,000 showed up to the caucuses.

If that trend holds, it will be disappointing to Democrats, who were hoping that a desire among those in their party to defeat President Donald Trump in November would produce a turnout closer to the nearly 240,000 who caucused in 2008.

The lack of a large turnout is the latest sign that Democrats may not be nearly as enthusiastic now as they were heading into the midterm elections.

You may recall that Democratic turnout in primaries was booming heading into the 2018 midterm elections. In fact, it was nearly triple the 2014 figure in competitive House primaries. This high turnout proceeded record turnout in the 2018 midterms and a wave election for Democrats in the US House.

Correlating presidential primary turnout with general election success is hard to do. Turnout is obviously lower when there isn't a competitive primary (i.e. at least two competitors going at it), and the number of contests that are competitive within a primary differs from year to year.

Still, the lack of high turnout in 2016 compared to a similarly long primary in 2008 did foretell problems for Democrats in the fall. If the pattern continues, it also calls into question any candidate who claims that he or she will be able to bring out new voters in the fall.

Some of the lower Democratic turnout in the 2020 Iowa Democratic caucuses could be because caucusgoers were overwhelmed by the large number of candidates (though there were plenty in 2008). Some of it could be that Iowa is becoming more Republican. Additionally, impeachment has caused the primary season to not dominate the headlines as it has in past years.

But we can look to other indicators to suggest enthusiasm is down for Democrats.

Look at the special elections compared to the Democratic baseline, for example. State legislative and congressional special election performance has correlated well with general election success over the last few decades. Oftentimes, that success is tied to advantages in turnout.

During the 2017 to 2018 period, Democrats were crushing it in special elections. They outperformed Hillary Clinton's margin by an average of 10 points, according to data compiled by Daily Kos Elections. They ended up outperforming her margin by about 7 points in the 2018 House elections.

Compare that to the 2019 to 2020 timeframe. Democrats are only outperforming their 2016 baseline by an average of about 2 points, a drop of 8 points from the 2017 to 2018 period.

We can also examine actual polling data about enthusiasm. CNN asks voters how enthusiastic they are about voting in the upcoming election.

In the final two polls before the midterms, Democrats and Democratic-leaning independent voters had an advantage over Republicans and Republican-leaning independents. An average of 65% of the Democratic group said they were extremely or very enthusiastic. This beat the average 58% of the Republican group.

Our last two polls for 2020 show something different. The 7-point Democratic lead on the extremely or very enthusiastic question has turned into a 7-point Republican lead on enthusiasm.

Now, you don't need to be an enthusiastic voter to cast a ballot. Common sense does suggest, however, that you'd rather have enthusiasm on your side.

Democrats may not have as much of an advantage on it than they used to.