Dow Jones & Company, Inc. / May 14, 2018

Pennsylvania, with the largest all-male congressional delegation, could nominate as many as six Democratic women in districts likely to be competitive in November.

All 18 of Pennsylvania’s members of Congress and both its senators are men. So are all five statewide elected government officials.

The state, one of four to hold primary contests on Tuesday, will serve as a test of whether the wave of Democratic women running can dilute one of the country’s most-durable male bastions.

“It’s a breaking of the old style of politics where it was just perceived that it was a man’s world,” said state Rep. Madeleine Dean, the front-runner in a Democratic primary for an open congressional seat in Philadelphia’s Montgomery County suburbs.

All told, Pennsylvania Democrats have 23 women running for House seats. Republicans have just one — Pearl Kim, a former state prosecutor who is unopposed for the GOP nomination in a strongly Democratic Delaware County district.

Emily’s List, the influential political group that backs Democratic women candidates who support abortion rights, has endorsed five women in Pennsylvania House races.

Most face stiff competition from male candidates, both in the primaries and later in November showdowns with the Republicans.

Pennsylvania has elected only seven women to Congress in its history, and three of them followed deceased husbands into office, according to the Pennsylvania Center for Women & Politics at Chatham University.

“It’s shocking to me,” said Chrissy Houlahan, an Air Force veteran running unopposed for the Democratic nomination in a district based in Chester County, in the suburbs southwest of Philadelphia. “I think it’s shocking to most Pennsylvanians as well. I don’t think any of us have a compelling reason for why it is.”

Terry Madonna, a Franklin & Marshall College professor who is an expert on Pennsylvania politics, said its male-dominated history is rooted in the state’s political patronage and high-paying state legislative posts. “We have a problem with men dominating the political structure of our state, and that’s been a tough tradition to break,” he said.

Pennsylvania’s congressional races are being contested under new maps instituted by the state’s Supreme Court in February. Due to retirements, resignations and congressmen running against each other for the same seat, seven of the state’s 18 districts have no incumbents.

Democrats, who need to flip 23 Republican seats to win control of the House, could net as many as six from Pennsylvania alone. The Cook Political report rates five GOP-held Pennsylvania House districts as toss-ups, leaning or likely to be won by Democrats. Two additional GOP-held seats are considered likely to be held by Republicans but competitive for Democrats.

Ms. Dean’s three opponents include Joe Hoeffel, who served three terms in Congress before leaving office to mount a failed Senate campaign in 2004. Mr. Hoeffel also ran for governor in 2010, but placed fourth in that year’s Democratic primary.

The winner will face Republican Dan David in a district Hillary Clinton carried by 20 percentage points in 2016. “Constituents here are excited about finally having some women in the delegation,” Ms. Dean said.

In Bucks County in Philadelphia’s northern suburbs, former Navy officer Rachel Reddick has been outspent 16-to-1 by Scott Wallace, a partially self-funding philanthropist whose grandfather was vice president under Franklin Roosevelt.

Ms. Reddick, who is backed by Emily’s List, has argued Mr. Wallace will be easily attacked by first-term GOP incumbent Rep. Brian Fitzpatrick in November because he lived in homes in Maryland and South Africa until he joined the campaign. Mr. Wallace, who was born and raised in the district and last year moved back into his childhood home, said earlier this year he last voted in the district in 1978.

Mrs. Clinton carried the district by two points in 2016. The Cook Political Report rates it a toss-up for 2018, though last week it dubbed Mr. Wallace “a badly flawed candidate.”

Ms. Reddick said Monday that it has been difficult to campaign against an opponent who can spend millions on his own race.

“Every candidate wishes they had more resources,” she said. “I do believe that our message is what’s going to come through.”

Republican officials involved in House campaigns say privately they are eager for Mr. Wallace to win Tuesday’s primary so their candidate, Mr. Fitzpatrick, and outside groups can use his residency against him. Mr. Wallace’s spokesman said the district is “eagerly supporting” Mr. Wallace. The Fitzpatrick campaign declined to comment on Monday.

Perhaps the most competitive Pennsylvania Democratic primary Tuesday is in the Lehigh Valley north of the Philadelphia suburbs.

Attorney Susan Ellis Wild is running in a six-way primary that includes two men.

One is Northampton County District Attorney John Morganelli, who after the 2016 election tweeted at President Donald Trump that he was “Pa. most senior prosecutor against illegal immigration waiting to hear from transition. Hope to serve.” In his TV ads, Mr. Morganelli now vows to “fight Donald Trump” in Congress.

Another is Greg Edwards, a pastor endorsed by Vermont Sen. Bernie Sanders. Mr. Sanders recently joined Mr. Edwards at a campaign rally in the district.

Mrs. Clinton won the district by a single percentage point in 2016. The Cook Political Report rates the race as Lean Democratic.

Republican voters in the district will choose between Dean Browning, a former Lehigh County commissioner, and Marty Nothstein, who won Olympic gold and silver medals in cycling events — events featured prominently on his campaign website.

Write to Reid J. Epstein at and Janet Hook at