While there weren’t any earth-shattering upsets in the Illinois primary election on Tuesday night, there were still more signs of a steady Democratic wave building in the fall.

Turnout among Democratic voters was up substantially over the past few midterm election cycles, according to several early reports, and more Republican voters stayed home. That is the recipe for Democrats to make big gains in the House and possibly the Senate this fall.

According to Politico’s Natasha Korecki, Democratic turnout in Illinois was up 300 percent versus 2014 and up 30 percent versus 2010, the last midterm cycle where there was a competitive Democratic gubernatorial primary. Meanwhile, Republican turnout dropped by 30 percent from 2014, when there was also a well-contested GOP governor’s race.

That has been the story of 2018 so far. As the Washington Post’s Philip Bump wrote in this great piece, Democrats have performed so strongly in the various special and primary elections because they have turned out at levels much closer to presidential years than their Republican counterparts.

Washington Post

In the Pennsylvania 18th District special election, Democrat Conor Lamb won 78 percent as many votes as Hillary Clinton did in 2016; his Republican opponent won only 52 percent of President Donald Trump’s vote share. In Texas, Democratic turnout for the state’s primary election was up 98 percent, while the GOP gained only 16 percent, as Vox’s Rachel Wolfe previously noted.

These turnout/enthusiasm gaps go hand in hand with wave elections — especially in midterms, when the party out of power tends to be motivated to come out and vote, while the party in power is less enthused. We saw a similar gap in 2006 (when Democrats took back both chambers of Congress) and in 2010 (when Republicans reversed the massive Democratic gains in the House of the previous election cycles).

Pew Research Center

So Illinois, a more conventionally blue state, is another good sign for Democrats. Turnout there Tuesday was stronger than we’ve seen in a decade — that’s what it’s going to take to pick up the 20 or so seats they need to win back the House.