Polls show Kavanaugh gave GOP an election boost. But it might not last.

One of the constants in recent election polling has been Democrats’ enthusiasm edge.

In Pennsylvania, that’s important; the swing state has several close congressional and state legislative races, and higher turnout among Democrats could put the party closer to retaking majorities in November’s midterm elections.

But in two new voter surveys, the advantage appears to have shrunk — and the likely culprit is partisan fervor over Brett Kavanaugh’s Supreme Court confirmation hearings.

A Quinnipiac poll from mid-September showed voters were 14 percent more likely to support a Democratic candidate for Congress.

Now, the number is halved.

And in July, a survey from NPR, PBS, and Marist College showed Democrats with a 10-point enthusiasm edge — a lead that is now down to two points.

Chris Borick, who runs Pennsylvania’s Muhlenberg College poll, said the reason is undoubtedly Kavanaugh.

“For Republican voters … that got their anger up, if you will, in terms of the election cycle and why it’s important,” he said.

But Borick’s not so sure the boost will last. He noted that midterm elections are “usually punitive to the president’s party.’

“I think everything shapes up in 2018 to hold form,” he added. “In other words, especially in House elections, there’s a wind at the back of Democrats.”