PITTSBURGH, PA.— Republican Tim Murphy resigned today from the U.S. House after allegations emerged that the long-term anti-abortion congressman had asked a mistress to have an abortion. His departure sets up a national showdown in a Western Pennsylvania swing district, where the number of Democrats outnumber Republicans.

Organized labor will likely pour millions of dollars into the race for the special election, and several labor leaders have indicated a desire to run. Unlike other special elections in the South and West, the Pittsburgh-area district has a history of flipping between Republicans and Democrats.

Currently, there are 70,000 more registered Democrats than there are Republicans in the district, but according to the Cook Political Index, the district tends to vote for Republicans by 11 percent.

The district includes the affluent suburbs of Mt Lebanon, the middle-class suburbs of the South Hils, and the deindustrialized union strongholds of Westmoreland County. It stretches all the way down to the West Virginia state line and includes many blue-collar communities where the principal means of employment are in coal mining and fracking.

(Full Disclosure: Payday Senior Labor Reporter Mike Elk’s grandfather, Regis Holden, was an elected Westmoreland County Democratic official).

A win in such a district, which has seen many working-class voters switch allegiances in the last decade, would be a major boost for organized labor.

Already, the 66-year-old retired Pennsylvania State Education Association union leader Mike Crossey has declared his candidacy for the race.

“I believe I made a difference in the classroom when I taught students, I believe I made a difference in Harrisburg when I fought Gov. Corbett’s school funding cuts and attacks on pensions,” Crossey told the Pittsburgh Post-Gazette in announcing his run, “and I believe I can make a difference in Congress because I’m able to work across the aisle with Republicans.”

Crossey previously was elected as an Allegheny County councilman for the area and, with the strong backing of teachers unions in the region, he could pose a serious threat.

Conor Lamb, the 36-year-old, Obama-appointed assistant U.S. attorney for the Western District, is also expected to resign this week as a federal prosecutor in order to run for the seat. Despite Lamb’s credentials as a drug prosecutor, Lamb plans to focus on criminal justice reform and solutions to the region’s opioid crisis.

Lamb comes from a prestigious Pittsburgh Democratic family. He is related to Pittsburgh City Controller Michael Lamb, a strong labor ally in the region and a major player in the Western Pennsylvania Democratic Machine.

As a Marine Corps JAG Officer, Conor Lamb was noted for his role in prosecuting military officers, who covered up sexual assaults and taking on the culture of rape in Okinawa. Currently, in the reserves, Lamb also has deep ties to the veteran community, which will help in securing support.

Other labor leaders and Democrats are also considering getting into the race.

On the Republican side, State Senator Guy Reschenthaler, a Tea Party conservative, has declared his intention to run.

A defeat for the GOP in the key Western Pennsylvania district could be a body blow for Trump.

Before the 2016 election, Pennsylvania had not voted for a Republican presidential candidate since 1988. If the GOP loses the seat, it could be a sign that Trump is losing his support among Rust Belt blue-collar voters.

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