Conservative election analyst Henry Olsen pushed back on President Trump Donald John TrumpSteele Dossier sub-source was subject of FBI counterintelligence probe Pelosi slams Trump executive order on pre-existing conditions: It 'isn't worth the paper it's signed on' Trump 'no longer angry' at Romney because of Supreme Court stance MORE's recent claim that there will be a "Red Wave" in November's midterms, saying history is on the side of Democrats.

"It is not going to be a red wave," Olsen, a senior fellow at the conservative Ethics and Public Policy Center, told Hill.TV's Joe Concha on "What America's Thinking."

He said it isn't a question of whether Dems will do well, it's a question of how well they will do.

"The only question we're talking about is the margin," he said. "We're not talking about whether or not Democrats are going to do extremely well. We know Democrats are going to do extremely well."

Democrats need to gain 23 seats to win back the House majority.

That appears to be within their reach. The Cook Political Report lists three GOP-held districts as likely being won by Democrats, and another seven as leaning toward Democrats. Only one House seat now held by a Democrat is seen as leaning or likely Republican.

In addition, another two dozen GOP seats are rated by Cook as toss-ups, compared to just three seats now held by Democrats.

The president's party typically loses seats in a midterm election. An exception was in 2002, when Republicans gained seats during the first midterm in George W. Bush's presidency a year after the Sept. 11 attacks.

Olsen said Republicans in Congress will need to convince enough voters to go against the grain and back their party again to withstand Democratic gains.

"If somehow the Republicans can play against type and say to some of these people, 'look, you may not like the president, but two years ago, you held your nose and voted for us. Do it again because the alternative is giving them power,' maybe they can pull something off," he said.

But, he added, "history is on the side of a large Democratic victory."

The electoral map does help Republicans in the Senate, as Democrats are defending more than twice as many seats as the GOP, including 10 in states won by Trump in the 2016 election.

— Julia Manchester