In the wake of Democrat Conor Lamb’s upset victory over Republican Rick Saccone in Pennsylvania’s deeply conservative 18th Congressional District this week, the GOP has yet another thing to worry about: Democrats have a 10-point advantage over Republicans in congressional preference in the 2018 midterm elections, according to a new NBC News/Wall Street Journal poll.

Fifty percent of registered voters say they would prefer a Democratic-controlled Congress, while 40 percent say they want Republicans to maintain control. That’s a change from a January NBC News/WSJ Poll that gave Democrats a six-point edge, 49 percent to 43 percent. And among independents, Democrats have a 12-point lead, with 48 percent of independents saying they prefer a Democratic Congress and 36 percent preferring Republicans.

Democrats also appear to have an enthusiasm advantage — 60 percent of Democrats and 64 percent of Clinton voters say they have a high degree of interest in the 2018 midterms. Fifty-four percent of Republicans and 37 percent of independents say the same. Young people, however, lag: Only 37 percent of registered voters ages 18-34 say they’re excited about the 2018 vote.

Republicans have a few reasons to be nervous about the 2018 midterms

Republicans dumped millions of dollars to hold Pennsylvania’s 18th District in a special election on Tuesday between Democrat Conor Lamb and Republican Rick Saccone. Trump carried the district, which won’t exist in November because the state’s Supreme Court redrew the map to tamp down partisan gerrymandering, by about 20 points in 2016. Lamb still eked out a victory over Saccone.

It is an ominous sign for the GOP of what might be to come in the November midterms. In a heavily Republican district, backed by $9 million, and with President Donald Trump having campaigned there just days before, the GOP candidate still couldn’t pull out a win. Other recent special elections that in theory shouldn’t have been close have been — Roy Moore vs. Doug Jones in Alabama, and Jon Ossoff vs. Karen Handel in Georgia, for example.

Moreover, the Pennsylvania special election was the first one where Republicans went all in on their tax cut message, touting the tax bill passed in December that insist will help them win elections in 2018 and beyond. As Vox’s Ella Nilsen and Tara Golshan note, Republicans initially focused on the tax cut messaging in Pennsylvania but by election day had pivoted to decrying so-called sanctuary cities after determining the tax message wasn’t breaking through. (Selling a tax bill that disproportionately benefits the corporations and the wealthy apparently isn’t as easy as anticipated.)

Democrats have consistently polled better than Republicans on generic Congressional ballots for months. According to RealClearPolitics’ generic ballot polling average, Democrats lead by 7.9 points. In December, RealClearPolitics had them up by about 13 points, but signs point to potentially major gains. Vox’s Andrew Prokop last year laid out how RealClearPolitics’ polling average has played out in actual elections:

2002: Republicans +1.7, minor change in Republican-controlled House

2004: Tied generic ballot, minor change in Republican-controlled House

2006: Democrats +11.5, wave flips House to Democrats

2008: Democrats +9, wave further increases Democratic House majority

2010: Republicans +9.4, wave flips House to Republicans

2012: Republicans +0.2, minor change in Republican-controlled House

2014: Republicans +2.4, gains in Republican-controlled House during national GOP wave

2016: Democrats +0.6, minor change in Republican-controlled House

Trump’s job approval is getting better. It’s still not helping the broader GOP.

Sunday’s NBC News/WSJ poll found that President Donald Trump’s approval rating stands at 43 percent among all Americans, four points higher than where it was in January. FiveThirtyEight’s average of presidential approval polls finds that 40.2 percent of Americans think Trump is doing a good job as president. On January 1, he was at 37.9 percent on average.

If voters are warming up to Trump slightly (and he still remains historically unpopular compared to his predecessors), that’s not translating to how they feel about Congress. “Trumpism may well help Donald Trump in his 2020 election, but the buck stops there — which is a flashing red light for Republicans in 2017 or 2018,” Democratic pollster Fred Yang, who conducted the NBC/WSJ poll with GOP pollster Bill McInturff, said in a statement accompanying the results.