Pennsylvania Democrats were bracing themselves to fight any Republican efforts to redraw the state’s congressional districts in a GOP-friendly way. They just didn’t expect to be fighting one of their own.

But that’s what happened Thursday, after the disclosure of a draft map backed by State Sen. Sharif Street showed the Philadelphia Democrat was working with a key Senate Republican on a plan that would boost his prospective congressional campaign. It would do that by drawing an incumbent Democrat and Republican together, creating an incumbent-free district in Philadelphia.

Senior Democratic operatives, already chafing at a House GOP map proposed just the day before, expressed deep concern over the new draft map, with some saying it would help Republicans take control of the House in next year’s midterm elections.

A campaign spokesperson for U.S. Rep. Brendan Boyle, the incumbent Philadelphia Democrat whose reelection bid would be complicated by the map, accused Street of “conspiring with Republicans to push a gerrymandered Republican map for personal political gain.” And U.S. Rep. Madeleine Dean, whose Montgomery County-based seat is seen as safe for Democrats, urged Gov. Tom Wolf to veto “the reported gerrymandered Congressional maps” if they reach his desk.

Street declined to discuss his political future Thursday but defended his negotiations with Republicans. It doesn’t reflect all his preferences, he said, but Democrats have an obligation to try to negotiate a map as part of the legislative process. And he said the map reflects his outreach to members of the state’s congressional delegation.

“It’s our job to negotiate the best that we can,” he said. “It would be an abdication of our duty not to try.”

It’s hardly an all-out war, and most Democrats agreed the proposal was unlikely to pass in its current form. But the intraparty squabble underscored how Democrats remain haunted by the last round of redistricting 10 years ago. That time, Democrats from Philadelphia and Pittsburgh worked with Republicans to pass a map that helped the GOP cement a 13-5 majority in the congressional delegation — even as swing-state Pennsylvania flipped from Barack Obama to Donald Trump to Joe Biden.

The map was so slanted toward Republicans that the Democratic-led Supreme Court, in an unprecedented move, threw it out just months before the 2018 elections. Under the map the court imposed instead, Democrats and Republicans each currently hold nine seats.

Some Democrats say their best prospects again lie with the high court drawing the final map and doubt any negotiation with GOP leaders will bear fruit in the high-stakes, zero-sum game of redistricting.

“Any Democratic elected official should be embarrassed to support a map as bad for Democrats as that map is,” said J.J. Balaban, a Philadelphia-based Democratic consultant who’s worked on U.S. House races.

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News of the map came hours after state House Republicans released their own redistricting proposal. Pennsylvania is losing a congressional seat because of population changes in the 2020 Census and will have 17 U.S. House members starting in 2023.

The final map must pass both chambers of the GOP-led legislature and be signed by Wolf.

A senior national Democratic official described both maps as Republican gerrymanders that are “obvious nonstarters.”

“It’s clear the Republicans have never taken this process seriously and are just running out the clock — it’s time for the court to step in,” said the official, who spoke on condition of anonymity to offer a candid assessment.

Street had for months been quietly negotiating a map with State Sen. David Argall (R., Schuylkill), the chair of the Senate State Government Committee, that they planned to introduce together as early as next week. Democratic sources said the Argall-Street map was still being finalized, but much of it was settled. Argall said Wednesday that he and Street had “made significant progress, but we still need some more time.”

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Street disputed suggestions that the map effectively trades a Democratic-held seat in Western Pennsylvania for a new Philadelphia-based district he could run in.

“Now, that’s just not true,” Street said, adding that the newly drawn district outside Pittsburgh would have similar demographics to the one Democratic U.S. Rep. Conor Lamb currently represents, and would remain competitive.

And Street criticized those in the party who want to split Pittsburgh to draw two safe Democratic seats. Street said that would lower the chances that a progressive like State Rep. Summer Lee — the first Black woman elected to the legislature from Western Pennsylvania who is now running for Congress — could win a seat.

“Black women, we say, are the backbone of the Democratic Party,” Street said. But some Democrats, he said, “want me to make changes to a district in a way to disempower the most successful Black female politician in the history of Western Pennsylvania. They want me to disempower her.”

“I understand we’ve got to balance the interests of making sure that we can win as many seats as we can, but we also have to be representative in the way we do that,” Street said. “And I think it’s been lost in the discussion.”

One Western Pennsylvania Democratic insider disputed Street’s insistence that the suburban Pittsburgh district would be winnable for the party. “Even Conor Lamb couldn’t win that seat right now,” the source said, describing it as “horrific.” (Lamb, a centrist Democrat, is now running for U.S. Senate.)

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Street said the map would eliminate a GOP seat by combining the current 12th and 15th Districts, and would also add more Democratic voters to the Chester County-based district represented by U.S. Rep. Chrissy Houlahan. Protecting Houlahan is seen as a key Democratic priority.

Democrats also hope to protect incumbent Democratic Reps. Matt Cartwright and Susan Wild in Northeastern Pennsylvania.

“Those seats are still swing seats, but they are competitive seats with roughly similar demographics to what they have right now,” Street said.

But multiple party officials and strategists said it would put a GOP-held Harrisburg-area seat out of reach for Democrats and questioned whether Wild’s Lehigh Valley district would actually become tougher to defend.

The draft map would break Philadelphia into four congressional districts, instead of the current three.

Most significant for Street, Boyle, who lives in Northeast Philadelphia and represents the eastern half of the city, would be drawn into the same district as U.S. Rep. Brian Fitzpatrick, a Republican who currently represents a swing district covering all of Bucks County and a small slice of Montgomery County.

The new Bucks County district would remain highly competitive in expanding into Northeast Philadelphia, a rare Republican-friendly enclave in the city. It would also be almost entirely new territory for Boyle, erasing much of his incumbent advantage — the vast majority of his current constituents would no longer live in his new district.

A Boyle spokesperson said the congressman will run for reelection in Philadelphia “regardless of what the final lines” of the district may look like.

The draft map also expands the current 3rd Congressional District, which covers the western half of the city and is represented by Democratic U.S. Rep. Dwight Evans, into part of Montgomery County. That seat would remain highly Democratic. And some portion of South Philadelphia would continue to be drawn into Democratic Rep. Mary Gay Scanlon’s 5th Congressional District, which would continue to cover all of Delaware County and also expand to take up about half of Chester County.

That leaves most of the eastern half of Philadelphia in a new 2nd District — with no incumbent.

Staff writer Jonathan Tamari contributed to this article.