But just as important, if not more so, there were marked differences between the parties in terms of the tone of their primaries.

On the Democratic side, there was bitter internal strife, dating back to the previous election cycle, between the “establishment” Democrats and the populist “Berniecrats.” Many of the latter are not committed partisans: While they are highly motivated to support populists, many refuse to lend their support to more conventional Democratic candidates. As we saw in 2016, many former Sanders supporters sat out the general election, voted for a third-party candidate or voted for Donald Trump.

Democrats should be concerned about their ability to mobilize populists in the races “establishment” figures won. So the party could find itself facing another enthusiasm deficit for many key races, even with Mr. Trump in the White House.

On the Republican side, there was clear unity behind the president and his party. The races were mostly about which candidate was most supportive of President Trump. As a result, it seems likely that Republican voters will support whoever is on their ticket in the general election.

We can count on Republican primary voters to turn out in November as well. Republicans reliably vote in midterms, and again it is important to note that primary patterns suggest that enthusiasm is particularly high in the Republican base this year, too.

Republicans are motivated, in part, to act as a bulwark against any “blue wave” that might be coming their way. Following Mr. Abbott’s lead, candidates like Senator Ted Cruz have been doing their best to reinforce expectations of a possible Democratic surge in order to get his voters fired up: “We know that the left is going to show up,” Mr. Cruz said on Tuesday. “The extreme left, they’re angry. They’re filled with rage. They hate the president.”