The “blue wave” that Democrats hope to ride to midterm glory has ebbed to a blue trickle, gleeful Republicans say.

Buoyed by a surging economy and President Trump’s rising approval numbers, the long-expected tsunami of Democratic victories in this year’s congressional elections has all but evaporated, says Senate Majority Leader Mitch McConnell (R-Ky.).

The GOP could even pick up six or eight Senate seats, he told The Hill on Saturday, and has a chance to topple powerful Democratic incumbents like Ohio Sen. Sherrod Brown — once in the running to be Hillary Clinton’s 2016 veep running mate and now said to be mulling a 2020 presidential run.

“I saw a survey within the last week in Ohio indicating that race is very competitive,” said McConnell. “I would certainly add Ohio to the list” of states where Democrats are suddenly vulnerable.

The party in the White House typically loses some seats in midterm elections — an average of 31 seats since 1976. And the figures are worse when the president has an approval rating under 50 percent, as Trump’s numbers have been.

The GOP’s narrow majorities in both houses mean that either or both of them could flip to the Dems if historical norms hold.

In December, generic-ballot polls gave Democrats as much as an 18-point advantage over Republicans in the 2018 elections. That spurred a record number of GOP retirements, with four senators and 27 representatives — including Speaker of the House Paul Ryan — throwing in the towel.

But in the last five months, positive economic news has revived Republican hopes. A Reuters poll last week saw the GOP with a slim one-point lead on the generic ballot.

The anti-Trump resistance movement could backfire in states like Nebraska and Pennsylvania, where last week’s primaries handed nominations to candidates who might be too left-leaning for their districts.

“They nominated some extreme people,” Rep. Steve Stivers (R-Ohio) told The Washington Post. “We nominated pretty mainstream folks that will be great candidates in the general election.”