PHILADELPHIA (TNS) — In Allegheny County, the longtime Democratic district attorney — a household name in Western Pennsylvania politics — is facing his first competitive election in years as a public defender runs as an independent.

In Philadelphia, progressive third-party candidates are waging a serious bid to claim City Council seats, potentially endangering Republicans and even Democrats.

Across Pennsylvania, insurgent progressive candidates are rattling the Democratic establishment in areas that have long been party strongholds, reflecting a broader national dynamic demonstrated in the rise of liberal politicians like Rep. Alexandria Ocasio-Cortez of New York, who beat an entrenched machine-backed congressman in Queens last year.

The races are being watched closely by officials and operatives in both parties who wonder whether third-party candidates have enough support to overcome inherent disadvantages in a two-party system.

“The Democratic electorate is not as progressive as they are, as a whole. But, because these groups are so well-organized, they are able to punch above their weight, so to speak,” said Mike Mikus, a Pittsburgh-based Democratic consultant, referring to the insurgents.

Some of the outsiders are offering bold policy proposals that are now part of the national political discourse, such as tackling mass incarceration and embracing a so-called Green New Deal to combat climate change. Others vow to change what they call an entrenched culture of corruption and cronyism, but otherwise focus on meat-and-potatoes issues like infrastructure.

Not all of the newcomers are favored to win, but the fact that they’re even running competitive general-election campaigns is evidence of discontent with the party establishment.

The results in Tuesday’s elections may leave clues about the party’s direction, just months before the first votes are cast in the Democratic presidential primary. One of the big questions Tuesday is whether Democrats can take control of county government in suburban areas such as Delaware County, which Republicans have run for generations. In these areas, Democratic elected officials tend to be more moderate than the activist left.

The political dynamic now facing Democrats is reminiscent of the rise of the tea party a decade ago, which pushed the mainstream Republican Party to the right, said T.J. Rooney, a former chairman of the Pennsylvania Democratic Party. “We’re starting to see that to a degree,” he said.

It didn’t happen overnight. Progressives were energized by Larry Krasner’s upset win in the Philadelphia District Attorney’s race in 2017, as the longtime defense attorney beat former prosecutors on a reform platform. And insurgents have been running against high-profile elected officials in the Pittsburgh area for multiple election cycles — and racking up wins.

Lisa Middleman, a public defender running as an independent for Allegheny County district attorney, is pushing a reform platform similar to Krasner’s. She is challenging incumbent Democrat Stephen Zappala Jr., who won a competitive Democratic primary and also ran a successful write-in campaign to win the GOP nomination.

That means Zappala — who’s held the office for two decades and is the son of a former state Supreme Court justice — will get votes from anyone who selects a straight-party ticket.

Zappala has the backing of the Democratic Party and organized labor. He hasn’t faced a competitive race until now, and observers say he’s run a lackluster campaign. Zappala has also drawn criticism for his handling of a case involving the fatal shooting of a 17-year-old black teenager named Antwon Rose II by a white police officer in 2018.

Middleman vows to end cash bail, halt prosecution for possession of marijuana, and hold police officers accountable. “Our district attorney is locking up people who struggle with mental illness and addiction, instead of the truly violent criminals that plague our streets,” she says in a campaign ad.

She’s getting a boost from other successful insurgent progressives like State Reps. Summer Lee and Sara Innamorato, who defeated two veteran Pittsburgh-area Democrats in state House primary elections last year. Along with State Rep. Elizabeth Fiedler of South Philly — who also beat a machine-backed candidate — Lee and Innamorato were endorsed by the Democratic Socialists of America.

“I do believe we are the folks who are able to really excite and expand the electorate,” Lee, who beat a 20-year incumbent, said in an interview. “That’s what our power is: bringing in people who for a really long time have felt disillusioned from politics.”