Trump and the GOP are desperate to win in the Pennsylvania special election, but the race may be slipping away.

It felt like the momentum has been shifting for months, and now it’s confirmed.

A new Emerson College survey reports that Democrat Conor Lamb is now out in front on Republican state Sen. Rick Saccone, ahead of next week’s special election in Pennsylvania’s 18th District. This is the first poll showing him in the lead.

Lamb, a former Marine and prosecutor, leads Saccone 48 percent to 45 percent, in the closely watched contest. The poll finds that Lamb’s supporters are more enthusiastic about the election, and Lamb enjoys a higher favorable rating than his Republican opponent.

All of this is rather shocking, given how deeply red the district has been in recent years. And if Lamb and the Democratic Party pull off an upset win next Tuesday, it would likely point to a political tsunami in November that could bury Trump and Republicans.

Note that Trump rushed to Florida in January to try to give a Republican candidate a boost, and Pence joined Saccone on the trail recently.

Meanwhile, direct donations to the Lamb campaign continue to pour in. He raised $3.3 million in the past two months, compared to his Republican opponent who raised just $700,000.

Scrambling, Republican groups have tried to prop up their candidate by unleashing outside money, outspending Democrats 17 to 1. But it’s not working.

A loss in the Pennsylvania district would be seismic. If Democrats win it will be because they flip white, largely working-class voters, who are seen as among Trump’s most loyal supporters.

Just 16 months ago, during the 2016 election, the working-class district looked custom made for Trump and his so-called populist appeal. He won there by 20 points.

And in terms of the Congressional race, it was even more lopsided: Republicans won in 2016 by 100 points because Democrats didn’t even bother to field an opponent to challenge incumbent Rep. Tim Murphy.

Last year though, Murphy, who is far-right and anti-choice, abruptly resigned after it was revealed he urged his mistress to get an abortion. That set in place the special election, which Republicans likely assumed would be a lay-up, in part because Democrats haven’t even run a candidate in Pennsylvania’s 18th District since 2012, when they captured just 36 percent of the vote.

Yet now, Democrats stand poised with a chance to claim the seat.

That’s what a blue wave looks like.