U.S. Rep. Conor Lamb will run unopposed in next month’s Democratic primary for the 17th Congressional District after his lone remaining challenger dropped out of the race Sunday.

Ray Linsenmayer, a consultant and Democratic activist from McCandless Township, announced Sunday that he suspended his campaign and is throwing his support behind Lamb.

The announcement means Lamb, who initially faced four challengers, will face off against U.S. Rep. Keith Rothfus in November’s general election for the right to represent the new 17th District.

The new district includes all of Beaver County, as well as most of Allegheny County and a part of Cranberry Township in Butler County.

At a press conference held in Carnegie on Sunday morning at Lamb’s campaign headquarters, Linsenmayer urged his supporters to unite behind Lamb for the November election.

“Conor Lamb has always shown himself to be a man of strong character and leadership, and has proven he can withstand any attacks the GOP throws at him,” Linsenmayer said. “While Rep. Lamb and I differ on some issues, we won't make progress on any of them without defeating Keith Rothfus and bringing new leadership to Congress.”

For his part, Lamb thanked his former opponent for his support and said Linsenmayer has been “instrumental” to the local Democratic Party.

“He is a passionate advocate, and I look forward to working together in this campaign and in strengthening the Democratic Party here in southwestern Pennsylvania in the years ahead,” Lamb said. “Democrats in the 17th district are united, we’re organized and fighting for every vote, and we’re going to win this together in November.”

In addition to Linsenmayer, Lamb had previously faced competition from Sewickley attorney Beth Tarasi and Erin McClelland of Harrison Township, Allegheny County, as well as former Shaler Area teacher Aaron Anthony.

Lamb, of Mount Lebanon, was officially sworn in as a congressman for the 18th Congressional District on April 12, after defeating Republican Rick Saccone in a special election in March.