PHILADELPHIA —The euphoria at Chris Rabb’s election night party last month hadn’t even started to wane before the democratic socialist and his supporters — dancing and hugging after capturing a rarely open Philadelphia seat in Congress — spoke of setting their sights even higher.

Taking on the city’s Democratic establishment to defeat a pair of more centrist candidates in the heated 3rd Congressional District race was a momentous win on its own. But the reckoning, they promised, wouldn’t be confined to Philadelphia’s borders.

“It’s going to change not just our city, but our entire commonwealth,” Rabb said in an interview amid the celebration at a Germantown banquet hall.

It was a sentiment echoed that night by key figures in Rabb’s coalition — from the head of the Working Families Party to Pittsburgh’s U.S. Rep. Summer Lee, the only other democratic socialist representing a part of Pennsylvania.

With the 2026 Pennsylvania Democratic primary in the rearview mirror, that conversation has broadly and quickly turned to the next biggest prize in the state: the U.S. Senate seat held by Democrat John Fetterman.

The senator has not said whether he will run for a second six-year term in 2028. But in an unusual situation for an high-profile elected official, a robust intraparty competition to replace him is expected to start either way in the next year as Fetterman increasingly sides with Republicans and as polls show that his support among Democratic voters has nose-dived.

Some Democrats who watched Rabb emerge from a competitive race, notching one of the left’s biggest wins yet in Pennsylvania, see an opportunity — one that extends the energy and momentum to boost a well-organized, progressive, anti-establishment candidate in the Senate primary.

Other strategists and activists say that’s a tall task, particularly in a swing state that rarely strays from electing more centrist politicians statewide.

“Anytime you have success, it breeds enthusiasm, which translates into more volunteers, into more money — everything you need to run a campaign,” said Mike Mikus, a Pittsburgh-based Democratic strategist. “But every election cycle is different. Every campaign’s different. The quality of candidates are different. And anybody who says that any one race signifies a permanent change within a party is mistaken.”

‘A huge impact on the political landscape of Pennsylvania’

In his campaign to succeed U.S. Rep. Dwight Evans, Rabb, a five-term state lawmaker, won 44% of the vote. He was up against State Sen. Sharif Street, who had the backing of the city Democratic apparatus, and physician Ala Stanford, a political newcomer endorsed by Evans.

Rabb and others have said his success, in part, was the culmination of a decade of progressive organizing that began in the city after U.S. Sen. Bernie Sanders’ 2016 presidential campaign.

That progressive infrastructure — the coming together of different groups to knock doors, make calls to voters, and unleash a significant independent advertising campaign in a way that rivaled the official Democratic Party organization — is likely the most important way that the left can use the experience of Rabb’s campaign to replicate its success elsewhere, strategists said.

It’s a template that could have “a huge impact on the political landscape of Pennsylvania,” said Rotimi Adeoye, a Philadelphia-based Democratic strategist who worked in the office of former U.S. Sen. Bob Casey.

In a district packed with Democratic voters, Rabb’s ability to turn out progressive voters should draw the attention of anyone looking to win the state’s Democratic Senate primary in 2028, Adeoye said.

“If a Democrat running statewide can learn from some of these organizational groups to build a strong, relational and community-based organizing campaign in Philadelphia and the surrounding suburbs in Montgomery County, Bucks County — they’re going to have a really big chance of winning,” Adeoye said.

In a sign that those efforts could coalesce around a Senate candidate, one of the groups that helped usher Rabb to victory remains the only major Democratic entity in the state to have publicly started laying the groundwork for a challenge to Fetterman.

The Working Families Party, which backed Fetterman in the 2022 general election after originally endorsing State Rep. Malcolm Kenyatta in the primary, said in November it would organize an effort to oust him. A “Primary Fetterman” website launched in January is equipped with a “Fetterman sell-out tracker” — highlighting his votes for Trump’s cabinet nominees and opposition to war powers resolutions that would rein in his military strikes, for example — and instructions for donors on how to request a refund from his campaign.

The website remains the extent of the group’s efforts so far to rally public support and back a new candidate, though its work is expected to pick up after this year’s midterm elections. For now, the party is looking forward to bringing new members who worked to elect Rabb into its fold.

“Our goal is always to keep building on the work we do each cycle and the success we have each cycle,” said Nick Gavio, the Working Families Party’s Mid-Atlantic communications director.

One PA, another statewide group in that progressive coalition, has not yet had internal discussions about the Senate race but it supports the Working Families Party’s position as a member of its steering committee, executive director Steve Paul said. He said more than 150 members of One PA mobilized for Rabb by talking to thousands of voters.

Winning a high-profile congressional race only helps add to that organizational infrastructure, making them “sharper for the next thing,” Paul said.

“I think it shifts what’s possible, politically — what people can envision,” he said.

Potential progressive roadblocks

Mikus said progressives have increasingly surpassed “more establishment Democrats” in their ability to run strong campaigns, including in his area of Western Pennsylvania where candidates like Lee have emerged in the last decade.

Democratic primary voters are also more progressive than they were 10 years ago, he said. But campaigning on a far-left — or a far-right — platform doesn’t often equate to success on a statewide level in Pennsylvania, a swing state where successful candidates tend to walk a “fine line” that appeals to both swing voters and a message that excites their partisan base, Mikus said.

“You’ve seen this time after time in presidential elections here in Pennsylvania,” Mikus said. “Hillary Clinton versus Bernie Sanders. Joe Biden versus Bernie Sanders. The vast majority of voters in Pennsylvania will go with the more mainstream Democrat.”

J.J. Balaban, a Philadelphia-based Democratic strategist and ad maker, said the party runs the risk of “drawing too big of a conclusion” based on a single election — particularly one like Rabb’s where candidates only needed to appeal to Democrats.

“Democrats really need to think hard about what it will take to win statewide in a purple state, which Pennsylvania clearly is,” Balaban said. “What it will take to win a general election in Pennsylvania is very, very different than what it will take to win in literally the most Democratic congressional district in the country.”

After recent years of tough losses — including the ousting of Casey by now-U.S. Sen. Dave McCormick, a Republican — Democratic voters will likely have a “tremendous thirst for candidates who have a credible case to make that they can win the general election,” Balaban said.

Fetterman, whose office did not comment for this story, has insisted that Pennsylvania’s purple state status means he should appeal to both sides of the aisle and not demonize the other side.

He’s also lamented the direction he sees his party going with candidates like Rabb, particularly around a growing sentiment that Israel has gone too far in its war against Hamas. Fetterman acknowledged last year that his unwavering support of Israel could cost him his Senate seat.

“Look at the people that are winning the primaries in our party right now, and look at their views on Israel,” Fetterman said at an American Jewish Committee conference in Washington this week.

On stage with McCormick and the head of the Jewish advocacy organization, Fetterman painted Graham Platner, the expected Democratic nominee for a U.S. Senate seat in Maine, as a “Nazi sympathizer” and connected him to Rabb.

“People also in our state, too. Rabb, he won, and he ran on being a very, very anti-Israel guy,” Fetterman said. “It’s actually a virtue [in the modern Democratic Party] ... It’s heartbreaking for me. And if it isolates me, then so be it.”

Who might run?

Of the Democrats widely considered to be eyeing a campaign to replace Fetterman, the public jockeying has so far been limited to criticisms of the incumbent.

U.S. Rep. Brendan Boyle, a moderate who represents the other half of Philadelphia next to Rabb’s soon-to-be seat, has repeatedly called Fetterman “Trump’s favorite Democrat.”

Former U.S. Rep. Conor Lamb, a moderate who represented a suburban Pittsburgh district before Fetterman beat him in the 2022 Senate primary, has frequently lambasted him.

And U.S. Rep. Chris Deluzio, who succeeded Lamb and leaned into progressive economic populism, has taken a less direct tack while noting the differences between himself and Fetterman over issues like Trump’s military interventions abroad. Deluzio has occasionally reposted others’ criticisms on social media — including one from Gavio, the Working Families Party spokesperson, last week that called Fetterman’s reversal on eliminating the filibuster “a new low” and “an indescribably massive backtrack from everything he ran on.”

None of the three have ruled out running.

Boyle is expected to weigh a Senate campaign vs. staying in the House to take a rare opportunity to lead the powerful budget committee if Democrats win the majority in November. Lamb, who’s remained highly active in Pennsylvania politics, said in an interview that he’s hoping to serve again and would run for office if he feels he “can be of service to the state.” Deluzio, who is also heavily involved in helping Democratic candidates across the state, said he’s focused on his reelection this year and that “we’ll see what 2028 holds.”

“I am not at all interested in seeing us lose this Senate election, and I certainly have gotten a lot of encouragement to look at 2028,” Deluzio said.

Progressives have also mentioned Lee, the Rabb ally who’s been a vocal member of the leftist wing on Capitol Hill while taking leadership roles in areas like securing the release of the Jeffrey Epstein files.

With potential candidates still several months away from making their decisions, it’s unclear who might try to take up the progressive mantle if Lee does not run, strategists say.

The field could also grow considerably. Other potential candidates could jump in, including the three other current Pennsylvania Democrats in Congress or former lawmakers like Susan Wild, who lost a swing congressional district in the Lehigh Valley in 2024. Wild said she’s “not ruling out” a run but she’s more interested in thinking about good female candidates in general since no woman has ever won a Pennsylvania U.S. Senate seat.

On the prospects of a battle between different factions of the party, Lamb said he believed Democrats had broadly learned a lesson — from Fetterman’s election in 2022, where he ran on being a reliable Democratic vote in the Senate — that was beyond ideological policy tests.

“Fetterman taught Democrats in Pennsylvania that you have to have a character test. Anybody can run around the state promising you these further left solutions, and that they’re going to be a thumb in the eye of the establishment, and they’re going to channel all your anger and dissatisfaction. And then that person can turn on you on a dime,” Lamb said. “The fact is that we have to evaluate our candidates based on whether they have integrity and they’re going to keep their word and, honestly, whether they have the work ethic to be a senator day in, day out.”

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