Colorado Republican Cory Gardner isn’t up for reelection until 2020 — but his recent poll numbers are another reason for him and Republicans nationwide to worry.

Gardner, who was elected to represent Colorado in the US Senate in 2014, has a 25 percent approval rating in his home state, according to a survey from the American Politics Research Lab released on Thursday. The survey, taken in November and made public just now, found that Gardner’s approval has dipped significantly from 43 percent in 2016 to 25 percent; it appears the senator has been weighed down by Washington politics.

Gardner has largely voted in line with President Donald Trump’s positions and appears to be hindered by the president’s low popularity nationwide. He has, at times, pushed back against the president — specifically when it comes to the Justice Department’s marijuana policies; Colorado has legalized marijuana — but that separation doesn’t appear to be breaking through to voters.

Democrats, unsurprisingly, widely disapprove of Gardner, with just 12 percent saying they think he’s doing a good job. But he also scores poorly among independents (23 percent of whom approve of his work) and Republicans (46 percent approve).

Ron Brownstein, senior editor at the Atlantic, noted that Gardner’s numbers should worry Republicans.

In a Dem-leaning but still competitive swing state, this poll puts Cory Gardner approval at 25% after he repeatedly votes with Trump agenda in 2017 https://t.co/GPv86cij9L — Ronald Brownstein (@RonBrownstein) January 27, 2018

According to FiveThirtyEight’s tracker of how Congress members vote with respect to Trump, Gardner’s votes line up with the president’s positions 93.4 percent of the time. He’s not the “Trumpiest” of senators — Sens. John Cornyn (R-TX), Orrin Hatch (R-UT), and Marco Rubio (R-FL), for example, vote more in line with Trump than him. But Gardner votes with Trump about the same amount of the time as Sens. Ron Johnson (R-WI), Rob Portman (R-OH), and Ted Cruz (R-TX).

All this said: Colorado is an increasingly left-leaning state, so Gardner’s poll numbers aren’t entirely shocking. Moreover, the American Politics Research Lab’s survey found other Colorado political figures’ approval ratings have dropped as well, including Gov. John Hickenlooper (53 percent approval, down from 58 percent) and Sen. Michael Bennett (44 percent approval from 53 percent), both Democrats.

Gardner isn’t up for reelection until 2020. Plenty of other Republicans are.

The Colorado survey is the latest in a string of data points that don’t seem to bode well for the GOP. The 2017 elections went pretty well for Democrats, who won governor’s races in Virginia and New Jersey, picked up 15 seats in Virginia’s Statehouse, and won a special election that gave them control of Washington’s state Senate. Down south, Democrat Doug Jones defeated Republican Roy Moore in Alabama’s special election for the US Senate.

And 2018 has thus far been kind to the Democrats, too. Earlier this month the party won a Wisconsin state Senate seat in a special election in a Republican-leaning district that went for Trump by about 17 points in the 2016 presidential election. Wisconsin’s Republican Gov. Scott Walker said in a tweet that it should be a “wake up call” for the state’s GOP.

Senate District 10 special election win by a Democrat is a wake up call for Republicans in Wisconsin. — Scott Walker (@ScottWalker) January 17, 2018

Democrats continue to have a lead in House generic ballot polling for 2018, though the most recent polling shows it shrinking. According to a RealClearPolitics average, Democrats still have a 7.9-point advantage over Republicans in 2018. Multiple Republican lawmakers have said they won’t be seeking reelection.

To be sure, the future isn’t all bright for Democrats, or dark for Republicans. It remains unclear how voters’ views of the recent government shutdown and who is to blame might weigh on future elections, or if it will even matter at all. And Democrats face a tough map in the Senate in 2018, with vulnerable seats in states such as Indiana, Missouri, and Nevada.

As Vox’s Andrew Prokop recently noted, the horizon for Democrats in the Senate could look brighter in 2020, when mostly Republican seats will be on the ballot. Both parties are gearing up for the 2018 midterm elections — the first nationwide referendum on Trump — and looking for any signs of how things will go. For now, Democrats seem to have the wind at their backs; Gardner’s polling shows that the president may be weighing the GOP down.