WASHINGTON — Rep. Jason Crow, a Colorado Democrat and former Army Ranger, had just ordered his second martini at a bar in Bucharest, Romania, when Rep. Nancy Pelosi, the former speaker, called him with an urgent question: How quickly could he get to Ukraine?

It was April 2022, weeks after Russia had invaded Ukraine and touched off an international crisis, and two Republican lawmakers had rushed to be the first to travel to the besieged country. Now Pelosi wanted to quickly arrange her own visit — and she wanted Crow, whose national security background distinguished him in his party, to come with her.

A late-night phone call from Pelosi to Crow would have been improbable when he first came to Congress in 2019. Hailing from a competitive district in Colorado, he had run as a centrist and avowed detractor of the liberal Pelosi, and after he knocked off a Republican incumbent he pledged that he would not vote for her for speaker.

But since then, his credentials — including three tours of duty in Iraq and Afghanistan and a Bronze Star, as well as a law degree and a background in private-sector investigations — have made Crow a go-to lawmaker for Democratic leaders on difficult national security issues.

Pelosi tapped him in 2019 to manage the first impeachment of President Donald Trump. He was part of the whip operation to rally support for legislation to send tens of billions of dollars in aid to Ukraine. He was selected as the top Democrat on a subcommittee investigating the Biden administration’s botched withdrawal from Afghanistan.

And last month, he was named the senior Democrat on a bipartisan task force to investigate the attempted assassination of Trump at a campaign rally in Pennsylvania.

“Political violence is intolerable, and we have to set a tone that it’s not appropriate for our nation,” Crow said of the assignment.

In his new role, Crow will work with Rep. Mike Kelly, R-Pa., chair of the task force, to get to the bottom of the law enforcement failures that preceded the shooting last month.

The two are racing to hire staff members and lawyers who can carry out the inquiry. They have a Dec. 13 deadline to finish the investigation and write a bipartisan report.

Creating the committee was a bit of an internal struggle.

Many Republicans clamored for seats, eager to demonstrate their loyalty to Trump, and there is much anger on the right from lawmakers who were not selected.

Rep. Matt Gaetz of Florida recently claimed that Speaker Mike Johnson had passed over two former military snipers — Reps. Eli Crane of Arizona and Cory Mills of Florida — for “disgustingly political” reasons related to their opposition to government spending. (The two were also among the Republicans who embraced conspiracy theories about the assassination attempt, baselessly suggesting that Trump’s political opponents had sought to kill him.)

Democrats were equally concerned about Republicans who were named to the task force, including Rep. Clay Higgins of Louisiana, who has also hinted that the left had a hand in the Trump shooting and has long trafficked in conspiracy theories about the Capitol attack on Jan. 6, 2021.

But Crow said he had confidence that Democrats and Republicans could come together to run a serious investigation. He pointed to the participation of several conservatives with military backgrounds.

“These are all serious people,” he said. “They’re conservative, of course, but I’ve worked a lot with them. They’re veterans, and they’re going to want this to be successful.”

On the Democratic side, there are two lawmakers who have been impeachment managers prosecuting Trump: Crow and Rep. Madeleine Dean of Pennsylvania. Now they are investigating how the Secret Service might have failed the man they once tried to remove from office.

Crow’s relationship with his party’s leaders started off rocky.

After vowing not to vote for Pelosi, he encountered an unusually aggressive lobbying effort by fellow Democrats — and even his neighbors — to persuade him to change his mind.

Crow refused, but he was upfront with Pelosi and kept her in the loop about what he was doing in Congress.

If he had an appearance in the news media and mentioned her, he had his staff send it to her.

Then at the end of 2019, Pelosi surprised Crow by summoning him to her office and asking him to be a manager in Trump’s impeachment trial. The president was charged with abuse of power for his efforts to persuade Ukraine to investigate and discredit his Democratic political rival, Joe Biden, and for obstructing a congressional investigation into his actions.

During the Senate trial, Crow became close with another member of the impeachment team: Rep. Hakeem Jeffries, D-N.Y., now the minority leader.

While Rep. Adam Schiff, D-Calif., spoke the most during the proceedings, Jeffries and Crow were the next most featured.

Jeffries has also frequently turned to Crow.

The Democratic leader temporarily reassigned Crow from the Armed Services Committee to a foreign affairs subcommittee to be the top Democrat on a panel created by Republicans to investigate the Biden administration’s disastrous withdrawal from Afghanistan in 2021.

Jeffries also asked Crow to be part of the whip operation to persuade Republicans and Democrats to back a huge aid package for Ukraine.

And when top Democrats were looking for someone to privately convey to Biden the seriousness of the party’s concerns about the national security implications of his age, that task, too, fell to Crow. In a private video call last month with members of the centrist New Democrat Coalition, Crow told the president that “many voters are losing confidence you can do this in a second term.” He asked what major change Biden could make to his campaign to turn things around.

The question elicited an angry response from Biden but had its intended effect, making clear that House Democrats felt they needed a new candidate to take on Trump after the president’s debate performance in June.

That evening, an assailant fired at Trump.

Days after that, Jeffries called Crow and quickly got to the point: Hey, I need you again. This time, it was to serve on the task force investigating the assassination attempt.

Crow has been getting to know Kelly as the two begin their work. He said he was promising to keep politics out of the effort and avoid hearings filled with grandstanding and name-calling, a break with recent proceedings in the polarized House.

“We want this to be less theatrical,” Crow said.