HELENA, Mont. — Senator John Walsh dropped his election campaign Thursday amid allegations he plagiarized large portions of a 2007 research project, leaving fellow Democrats to scramble for a replacement with the election less than three months away.
Nationally, the development only improves the odds for Republicans, who need a net gain of six seats in November to take Senate control. Even before Walsh’s exit, strategists in both parties considered his Senate race against Representative Steve Daines an opportunity to tip one more seat in Republicans’ favor.
The Montana Democratic Party must hold a nominating convention before Aug. 20 to choose a replacement candidate.
Former governor Brian Schweitzer’s name circulated as a potential contender even before Walsh’s announcement. But Schweitzer rejected a run earlier this year, when he said he wasn’t interested in the seat that opened when Max Baucus, a six-term senator, was named US ambassador to China.
Walsh, a former National Guard commander, said in a statement to supporters that he was leaving the race but will keep the seat he was appointed to until his term ends in January 2015.
He said the controversy surrounding his US Army War College research paper had become a ‘‘distraction from the debate you expect and deserve.’’
‘‘I am ending my campaign so that I can focus on fulfilling the responsibility entrusted to me as your US senator,’’ Walsh said.