Three new Democrats have officially joined the race for a redrawn 5th Congressional District that now encompasses Delaware County and South Philadelphia. Seven other challengers are also gunning for the district – but sources say as many as another half-dozen challengers could be waiting in the wings.

Chester Mayor Thaddeus Kirkland and public school teacher Larry Arata both filed paperwork to run last week. And on Monday, former Deputy Mayor of Philadelphia Rich Lazer formally kicked off his candidacy.

Additionally, attorneys Dan Boyle, Mary Gay Scanlon, Ashley Lunkenheimer and Dan Muroff have all filed paperwork with the Federal Elections Commission to run in the new district. So have two doctors – Julie Eble and Molly Sheehan – professor Mary Ellen Balchunis, former CIA officer Shelly Chauncey and Radnor Democratic Committee Chair George Badey.

The list of potential challengers doesn’t stop there. Former Morgan Stanley employee Lindy Li, journalist David Wertheim and state Rep. Margo Davidson have all expressed interest in a bid.

Notably, Boyle, Li and Sheehan do not reside in the district – and Lazer, a South Philly native who is backed by powerful labor unions, is the sole entrant that resides in a small portion of the new district that covers part of Philadelphia.

Lazer had previously announced his intent to run against incumbent U.S. Rep. Bob Brady in the old 1st District, when it encompassed a sliver of Delaware County and a large section of Philadelphia. But a new court-ordered congressional map turned that calculus on its head – only about 16 percent of the new district lies in Philadelphia.

Some sources said Lazer could risk opening a feud between powerful political factions in the city and the suburbs, others that his spot as the sole city resident running against a split field of suburban candidates could give him an edge.

A spokesman for Lazer downplayed the political chatter.

“It’s about working families first,” said Gabriel Roberts, communication director for the Lazer campaign. “He’ll get as much support from working families in Delaware County as he will in Philly. They want the same things, like safe streets and economic equity.”

While the new district favors Democrats, the potential GOP field is nearly as crowded. Radnor Commissioner Richard Booker, volunteer firefighter Joe Billie, developer Wally Smerconish, attorney Jeremy H. Gonzalez Ibrahim, Pearl Kim, Greg McCauley and Clare Putnam Pozos are also running for their party’s nomination. However, only Billie and Pozos have filed paperwork declaring their candidacies.