Many people in Washington were surprised when May’s debt ceiling negotiations quickly narrowed down to House Speaker Kevin McCarthy, his lieutenants and top White House aides. Not Sen. Kyrsten Sinema (I-Ariz.).

In fact, it was sort of her idea.

“I did suggest to the White House that meetings would be more productive if the people who actually had the authority to make a deal and deliver the votes were the only ones in the room,” Sinema recalled in an interview.

Senators typically loathe the sort of top-down negotiations that produced the deal to lift the debt ceiling through 2024, preferring to use the chamber’s notorious bipartisan gangs that give them more direct input. And this time around only a handful of rank-and-file lawmakers were able to directly influence the process, most distinctly Sinema and Sen. Joe Manchin (D-W.Va.).

The deal was pretty much exactly where the two senators hoped everything would end up — alienating only the far right and left and empowering the center.

“It’s a wonderful deal when you have the extremes back in the minority,” Manchin said.

The two centrist senators barely entered the public debt narrative other than pressing for negotiations. Yet each played an integral role in jump-starting discussions and assembling the particulars of the deal, particularly the legislation’s work requirement, spending and energy provisions.

Sinema leaned on years of relationships with McCarthy and lead negotiators Reps. Garret Graves (R-La.) and Patrick McHenry (R-N.C.) while also consulting closely with OMB Director Shalanda Young and White House counselor Steve Ricchetti, who led the White House strategy alongside Legislative Director Louisa Terrell. She spent Thursday racing around the Capitol, aiding Senate leaders as they sought an agreement to speed votes up, spending literally hours helping craft joint statements and locking in amendment votes.

She got used to playing the hectic role of shuttle diplomacy over the past month. Last week, as Sinema was getting ready to appear on Fox News during a visit to the Arizona border, her cell phone lit up with separate calls within a few minutesfrom several major debt players: McHenry, Young and Senate Majority Leader Chuck Schumer.

“I was talking with everyone all the time,” Sinema recalled.

Manchin credited Sinema with utilizing friendships from her past life in the House to get things rolling. The former governor had a different lane.

The West Virginia moderate coordinated with centrist Democrats in the House on messaging and spoke to both McCarthy and Schumer about modest ways to rein in spending. He finally got the framework very few in his party wanted just a month ago: some spending restraint, and yes, approval of the Mountain Valley Pipeline.

The two centrists often publicly thwarted progressives’ agenda during the first two years of Joe Biden’s presidency, but most of their work this episode occurred behind the scenes. In some ways it’s a capstone to the two senators’ outsized imprint on government: Though they have other unfinished priorities, the debt limit negotiations may be their top accomplishment during this term’s split Congress — as both consider reelection runs.

Manchin’s public restraint regarding inclusion of the pipeline was intentional: He worried it could poison the provision. He remembers all too well the GOP voting down his energy permitting reform bill after Democrats’ party-line climate, health care and tax bill passed last year.

“For them to go out from the beginning and say, ‘OK, we gotta get this in for Manchin?’ That wasn’t a strategy that I thought would be helpful,” he said in an interview. “Republicans had to be where that’s going to be planted from their side.”

Sen. Shelley Moore Capito (R-W.Va.) called the pipeline’s inclusion in the debt deal a “team effort” and spoke to Graves, McCarthy and others to push for the pipeline. One of Manchin’s potential Senate race rivals, Rep. Alex Mooney (R-W.Va.), voted against the debt deal.

Manchin also advised both Schumer and McCarthy on how they might handle modest budget caps. It didn’t go over well with Democrats at first.

Sen. Joe Manchin coordinated with centrist Democrats in the House on messaging and spoke to both House Speaker Kevin McCarthy and Senate Majority Leader Chuck Schumer about modest ways to rein in spending.