It’s not just a big and arbitrary benchmark for the president. Thursday also marks the 100th day in office for the youngest Democrat to serve in the U.S. Senate since Joe Biden, who assumed office in 1973 at the age of 30.

Jon Ossoff is used to being the center of attention. First, as a candidate in a 2017 special House election, then running in Georgia’s Senate race against Sen. David Perdue (R-Ga.), and now as a freshman senator. Ossoff, along with friend and peer Sen. Raphael G. Warnock (D-Ga.), were both sworn in on the same day as Biden after winning hugely significant runoff elections in the Peach State.

The victory by the Georgia Democrats handed Biden control of the Senate, allowing the White House to envision and attempt a much more ambitious agenda, unveiled Wednesday night in a speech to Congress. Whether Ossoff succeeds is also a test of whether Biden’s go-big message will prevail with 2022 voters.

The Georgia senators have served as the enforcers of the centerpiece of the Biden administration’s $1.9 trillion economic stimulus plan: the inclusion of $1,400 stimulus checks to many Americans hit hard by the coronavirus pandemic. The checks were the first economy policy-related items Biden mentioned Wednesday night. And on Thursday, in another sign of Georgia’s political relevance, the president and the first lady will visit the state.

Helping sweep the Democrats into power doesn’t mean Ossoff has avoided controversy. He has found himself in the middle of several thorny debates given his place in the 50-50 Senate, meaning every vote could mean victory — or defeat — for Biden.

Ossoff and Warnock have been reliable champions for Biden’s progressive agenda, urging swift action on the stimulus payments by arguing they had to deliver on their campaign promises. Ossoff also helped broker a deal reached last month between two South Korean battery companies locked in a bitter trade dispute to avoid torpedoing one of the biggest economic investments in Georgia’s history.

“There was a real recognition and appreciation that Rafael and I had delivered the majority and that none of this — I mean none of this — would be possible had we not prevailed,” Ossoff told The Washington Post in an interview, adding his new colleagues welcomed what he described as an “assertive and outspoken” approach to passing the stimulus package “from the new guy.”

But the 34-year-old millennial — who is up for reelection in 2026 after winning by 1.2 points last year in a state Donald Trump still claims he won — has been criticized by activists and progressives for not calling to eliminate the filibuster entirely. (They want him to ramp up efforts to assure the passage of voting rights legislation.) Senate rules require 60 votes for almost any piece of legislation.

Democrats “must be willing to consider changes to Senate rules to protect voting rights, and I remain open to changes to the Senate rules to protect voting rights,” he said Wednesday. Ossoff declined to say whether he’d ask Biden to overhaul the filibuster to expand voting rights.

“My conversations with the president are confidential and whenever he and I have anything to announce together, we’ll announce it,” he added. “But I’m gonna maintain the confidence of my discussions with the president and his senior staff.”

Ossoff is also calling on Senate Democrats to quickly approve the administration’s massive two-part infrastructure package. He called it a rare opportunity “to have a generational impact,” in a move that could cost $4 trillion and would be partially paid for by taxes on rich individuals and corporations.

“We have a once-in-every-few-decades opportunity right now, and we cannot squander it,” Ossoff added. “And that’s why I am so adamant that we need to go fast and we need to go big with a historic infrastructure and clean energy plan.”

Republicans have balked at the price tag for those proposals, however, with Senate Minority Leader Mitch McConnell (R-Ky.) calling Biden’s overall policies “catnip for the liberal base" instead of things that can be crafted with Republicans.

Ossoff defended Biden’s approach to bipartisanship, and the president’s use of a procedural tactic known as budget reconciliation to push through his agenda with only Democratic votes.

“I think [Biden] has bent over backwards to be receptive to Republican ideas and to offer them the opportunity to weigh in,” Ossoff added. “And ultimately we have to do what we believe is right for the people. And if that means using reconciliation to pass the stimulus or a historic infrastructure bill, that’s what we should do.”

Some Democrats, like Sen. Joe Manchin III (D-W.Va.), have also thrown cold water on the infrastructure package and praised Republicans’ scaled-down proposal.

Ossoff seems to have become something of a Manchin whisperer during his short time in Congress. The 73-year-old West Virginia Democrat and the first-termer have developed a close relationship and the two have collaborated on a number of issues, according to Ossoff. Manchin notably was skeptical of another round of direct payments in the stimulus package but eventually came around to supporting the relief package.

Ossoff defended Manchin on voting rights, even as other prominent Democrats, like House Majority Whip James E. Clyburn (D-S.C.), have criticized him for being the lone Democratic senator who did not sign on as a co-sponsor of the voting rights package the House passed in March.

Those who know Ossoff are unsurprised by his rapid rise. Rep. Josh McLaurin, a Democratic member of the Georgia House, recalled meeting Ossoff at a coffee shop that served beer in 2017 when they were primary opponents. McLaurin, who went to scope out the competition, recalled wearing jeans and ordering a beer, while Ossoff showed up in a suit with his deputy finance director.

“Jon was just as focused and just as down to earth as he appeared to be and he’s never wavered in that personality since,” said McLaurin. “His approach to governing appears to benefit from the same skill set.”

Ossoff has been careful to take care of things back home while cultivating a national profile.

He was one of few Georgia lawmakers who remained publicly neutral during the trade dispute between SK Innovation and LG Energy Solution. Behind the scenes, however, he was engaged in rounds of negotiations with both companies and was ultimately credited by LG Energy Solution’s top executive for brokering a deal.

The settlement, which was supported by Georgia Republicans and Democrats alike, not only solidified at least 2,600 new jobs at two battery production plants in a politically red part of the state. But it also ensured Biden’s ambitious zero emission transportation goals weren’t threatened by a weak supply chain that’s made it challenging for automakers to source enough batteries to scale up production.

“It feels like we have someone who is future focused and making sure that the South, and Georgia specifically, is a part of the march towards a clean energy economy,” said Nsé Ufot, the CEO of the New Georgia Project.

Ossoff has also attracted attention in Washington by using his extremely online presence to help constituents navigate the confusing process of receiving stimulus benefits.

“We want to meet people where they are, so if that means doing outreach to constituents who have issues because of a comment that my team saw on TikTok, or sending our outreach representatives out into the field to meet with seniors at senior centers — we have to reach people across the range of places,” said Ossoff.

Savannah’s Democratic mayor, Van Johnson, said Ossoff’s approachable style is reminiscent of the late civil rights leader and Georgia congressman John Lewis (D-Ga.), Ossoff’s former boss and mentor.

“I think he would be smiling — I think he’d be dancing because to think that both of these men had close intimate connections with John [Lewis], who did not get to see his pastor and protege making history," said Johnson, referring to Warnock and Ossoff. “That speaks to the legacy of John Lewis that continues in Georgia."