WASHINGTON — In the span of one hour Tuesday, House Democrats moved to impeach President Donald Trump for abusing his office and simultaneously delivered his biggest legislative win of the year by agreeing to a long-stalled trade deal — a dramatic clash of two issues that will define the president’s legacy and the 2020 election.

Even for the chaotic and unpredictable Trump presidency, the contrasting events marked an odd moment as Democrats worked to advance the biggest trade pact in a generation with a chief executive they accused Tuesday of such heinous acts that he’s likely to become the third U.S. president impeached.

But the timing was likely no accident, and both sides have strong motivations for working together despite, or maybe even because of, the bitter political war over impeachment.

For Trump, securing Democratic support for the U.S.-Mexico-Canada Agreement puts him on the verge of fulfilling one of his biggest campaign promises — to replace the reviled North American Free Trade Agreement — just as he prepares to face voters again in 2020.

For Democrats, the conflicting images bolstered their claim that they didn’t come to Washington merely to fight Trump — that they can “walk and chew gum,” to cite a claim repeated by Democrats for the past several weeks. Democrats insisted the timing — unveiling impeachment articles as they announced agreement on a revised NAFTA — was not planned.

“Sometimes they coincide — there’s not much you can do about it,” said Chairman Richard E. Neal, D-Mass., who, as chairman of the House Ways and Means Committee played a role in both impeachment and the trade deal. “I repeatedly noted that when we got the agreement (on the trade deal), we would go with it. We got the agreement, we’re going with it. So you can’t control the timing.”

For voters, the dueling announcements offered a glimpse into an alternate reality, a real-time contrast between the embattled presidency that Trump now has and the one that might have been — in which a political outsider cuts across party lines to deliver a trade deal.

“The split screen mirrored what’s going on in our politics,” said David Gergen, an aide to presidents in both parties dating to Richard Nixon. “The Democrats see a man who is unfit for office and should be thrown out, and Republicans see a man who just scored a major breakthrough on trade.”

The trade deal highlighted how much more Trump could have accomplished “had he stuck to the national agenda,” Gergen said. “Instead this became all about him. It’s sucked a lot of oxygen out of the system.”

That the two events happened an hour apart was all the more jarring. When a reporter asked House Speaker Nancy Pelosi, D-Calif., about the “whiplash,” she interjected, “And the day is young.”

The whiplash is likely to continue in Congress’ two-week sprint before Christmas. Democrats — and Republicans — want to notch legislative victories they can tout at home. Lawmakers and the White House cobbled together a deal to fund Trump’s Space Force in exchange for implementing paid family leave for federal workers as part of a defense funding bill. Top lawmakers in both parties held a meeting in Pelosi’s office Tuesday with Treasury Secretary Steven Mnuchin to discuss how to keep the government funded past Dec. 20.

And a group of Republicans and Democrats have written new legislation to prevent “surprise” medical bills, a hugely populist issue. However, the bill has yet to win support from Sen. Charles E. Schumer, the Senate minority leader, and other Senate Democrats amid strong opposition from hospitals.

The legislative crush to meet year-end deadlines is an annual tradition in Washington. But the rush — and bipartisanship it requires — is all the more important this year as Democrats try to ensure they have legislation to balance out impeachment.

For both parties, the issues debated Tuesday likely will have a major impact on the 2020 campaigns.

Democrats in the progressive wing of the party have been arguing for years that the president needs to be held accountable, a clamor that only amplified in the wake of his attempt to get Ukraine to investigate his political rivals. If the House hadn’t moved to impeach, Democratic enthusiasm that propelled the party in the 2018 election would likely have suffered.

But moderate Democrats have also been itching for bipartisan victories such as the trade deal, which will bolster the party in farming communities, such as California’s Central Valley.

The trade agreement stands to be one of the only major pieces of legislation that gets through the divided Congress this year and to Trump’s desk. Freshman Democrats, many of whom unseated Republicans in areas of the country where the president is relatively popular, have been privately begging Pelosi for victories like this that they can tout to their constituents.

One of the House’s most progressive Democrats was critical of the idea of passing a deal to merely appear productive and bipartisan.

“Personally I am not thrilled with how this has developed, but I understand that there are more conservative members of the party, that they want to communicate to their constituents that we are ‘doing something’ while impeachment is happening,” said Rep. Alexandria Ocasio-Cortez, D-N.Y. “And so I think some members from swing districts … believe that this is a signal to their constituents that they are able to work with the president.”

The president stands to benefit, too, of course. The House — or “do-nothing Democrats” as he says — will serve as a foil in his race for reelection. And while moderate Democrats can run on USMCA, so can the president. The deal will hand Trump his biggest accomplishment since the 2017 GOP tax deal.

Republicans faced a similar tension in the 1996 presidential election. Republican members of Congress were eager to show bipartisan accomplishment, working with Bill Clinton to pass a measure that overhauled the welfare system. The party’s presidential nominee, Sen. Robert Dole, saw the measure as valuable bragging rights for Clinton.

Tim Murtaugh, director of communications for Trump’s reelection campaign, argued that although Pelosi didn’t want to give Trump a political victory, she realized that her members needed the trade deal just as much.

“She can read the polls just like anyone else could,” he said. “Naked partisanship is not what Americans want.”

Republicans say Democrats used the trade deal to blunt what they call the sinking popularity of impeachment.

“After announcing impeachment, within less than an hour, the speaker finally relented and said she would bring USMCA up,” said House Minority Leader Kevin McCarthy, R-Calif.

Democrats dismissed such speculation. “This is good for our country. This is good for our economy — nothing to do with Trump,” said Rep. Henry Cuellar, D-Texas, of the trade deal.

Rep. Elissa Slotkin, D-Mich., who represents a district that Trump won in 2016 and was one of the last Democrats to support an impeachment inquiry, said the debate over timing was a “total Washington conversation” that won’t matter to her constituents who want the new trade deal. “I’m just thrilled to have that done,” she said. “I don’t care about the timing.”

The clash even prompted some confusion in Congress, where lawmakers largely deal with one issue at a time and have certain issues they want to talk about — or don’t.

“We’re ready to rock and roll,” Cueller, a longtime booster of the trade deal, shouted to reporters upon exiting a meeting of House Democrats on Tuesday morning.

Then he quickly added, “I’m talking about trade.”