Pennsylvania House Rep. Summer Lee could become the latest addition to the Squad if she wins her Democratic primary on Tuesday.

Lee, one of six challengers backed by the Justice Democrats, a progressive PAC, is running to fill an open seat in Pennsylvania’s 12th Congressional District vacated by Rep. Mike Doyle. It’s a safe Democratic seat that includes Pittsburgh and the surrounding suburbs, and it’s poised to be a key pickup for progressives, should Lee win her race this week.

Lee is currently up against four other candidates in the race, including attorney Steve Irwin, who’s backed by Doyle and many establishment Democrats in the area. Lee, meanwhile, has the support of local progressives as well as national leaders like Rep. Alexandria Ocasio-Cortez (D-NY) and Sen. Bernie Sanders (I-VT).

There’s little publicly available polling on the race, but a recent poll from Emily’s List, which endorsed Lee, has her leading the field (many voters in the survey, however, were still undecided). If Lee were to win, her victory would help progressive Democrats continue to build power in Congress: In 2020, candidates including Reps. Cori Bush (D-MO) and Jamaal Bowman (D-NY) won their races, bolstering the party’s left flank.

Given Austin city council member Greg Casar’s primary win in Texas’ 35th Congressional District, a safe seat for Democrats, a Lee win would give House progressives at least two new members. And with increased numbers comes increased sway over policy, or, if the GOP retakes the House, greater ability to shape how Democrats respond to a Republican majority.

Gains in the progressives’ bloc in 2020 enabled the group to have more leverage over what policies to focus on and the timing of key votes this term. For example, progressives initially delayed a vote on the bipartisan infrastructure bill in order to push consideration of social spending legislation. In 2022, progressives are eyeing more victories in places like Pennsylvania, Texas, and New York — all of which could help them strengthen their hand even further.

Summer Lee has helped build a progressive movement in western Pennsylvania

Lee is a progressive in the mold of many Squad members: She backs more ambitious policies including Medicare-for-all, a Green New Deal, and packing the Supreme Court. She has emphasized, too, her own experiences with issues like air pollution, and the need for systemic change in order to promote environmental justice.

Irwin, Lee’s main competitor, has taken a more moderate stance and stressed his commitment to working with Democratic leadership and building broad coalitions to pass policy. The difference has been evident on subjects like climate: While Lee has focused on promoting a transition to renewable energy, for example, Irwin was the only candidate in a recent debate to talk about the ongoing role of natural gas.

“In a lot of ways, that race ends up reflecting many of the same clashes that are visible in the rest of the Democratic Party,” said Allegheny College political science professor Tarah Williams. “There’s a big conversation between the two campaigns about how much compromise needs to happen in order to get policy achieved.”

Recent tension in the race has centered on millions in outside spending on political ads, including those paid for by AIPAC’s super PAC, a pro-Israel group backing Irwin. The AIPAC- affiliated group has expressed concern that Lee wasn’t supportive enough of Israel, something she has pushed back on, while defending past remarks she’s made about the country’s treatment of Palestinians.

The ads, which have been widely criticized by local leaders as well as Sanders, question Lee’s backing of President Joe Biden. Notably, however, they leave out the fact that Lee campaigned for Biden in the general election.

In addition to being the only woman and elected official running in this primary, Lee would be the first Black woman to represent Pennsylvania in Congress if elected. Her candidacy builds on a burgeoning progressive movement that she has helped foster in western Pennsylvania.

“There is a movement there in Allegheny County to move on from the old guard of leadership that’s been there for decades,” says Justice Democrats’ spokesperson Usamah Andrabi.

Lee could help expand progressive power in Congress

A Lee victory would help grow progressive power in Congress, adding to recent wins in this cycle and last.

In addition to Casar’s win, progressive immigration attorney Jessica Cisneros was able to force Rep. Henry Cuellar into a runoff for Texas’ 28th Congressional District. Justice Democrats have also backed organizers Kina Collins in Illinois’ Seventh District, Rana Abdelhamid in New York’s 12th District, and Odessa Kelly in Tennessee’s Seventh District in upcoming primaries.

Six new staunch progressives could seriously strengthen progressives’ influence in Congress. This term, progressives were able to have more sway given Democrats’ narrow majority in the House. They’ve used that power to push for more expansive stimulus checks and to bargain for more aggressive prescription drug legislation.

If Republicans retake House control, as they’re widely expected to, progressive power would be somewhat diminished, as Democrats would no longer control the agenda. However, they’d likely play a key role in leading Democrats’ anti-GOP messaging, and helping to counter investigations of the Biden administration as well. In the past, progressives were among the first to begin pushing for Trump’s impeachment and among the most vocal opponents of policies like family separations.

With greater numbers, progressives would be able to mount even stronger rhetorical campaigns to push back against a GOP-controlled House. They’d also be able to put more pressure on party leaders to take these types of stances.

New progressives like Lee could also bolster the subgroup of more liberal members within the Progressive Caucus, known as the Squad. Currently, the Squad includes Reps. Alexandria Ocasio-Cortez, Rashida Tlaib, Ilhan Omar, Ayanna Pressley, Jamaal Bowman, and Cori Bush. If all six Justice Democrat candidates win this cycle, its size could double, giving them more sway as a bloc within a bloc.

With the exception of Cisneros, the challengers are also in safe Democratic districts, meaning they could have a long-term impact on the ideology and priorities of the Democratic Party if reelected. “The bigger the bloc, the bigger the potential you have to have weight in the Democratic Party, the stronger your negotiating power,” says Leah Greenberg, a co-executive director of progressive advocacy group Indivisible.

In the past, members of the Squad have broken from the broader Progressive Caucus membership. When a vote was held on a bipartisan infrastructure bill last year that decoupled it from a vote on a larger social spending bill that included a tax cut for families with children and funding to fight climate change, for instance, all six lawmakers voted against it. Progressives hope that in similar situations in the future, those six lawmakers will have even more company.

“I think about all the communities in Pennsylvania that have not seen the type of representation that I’m looking to bring and to offer — folks who will value and really lift up poor working folks, and Black and brown folks, and I recognize there’s a cohort of people who’ve already been fighting for that,” Lee said in an MSNBC interview. “And it would be an honor to join that.”