Massachusetts state Rep. Thomas Conroy (D) dropped his bid for the Senate today, leaving presumptive nominee Elizabeth Warren an almost perfectly clear path to the Democratic nod to take on Sen. Scott Brown (R) in 2012.

Conroy, who gained local fame by walking more than 650 miles across the Bay State as part of his campaign, said he would run for re-election to his state House seat instead.

“[A]fter much reflection, it is clear that, while support for my candidacy has been generous, we could not run the kind of campaign we needed to run throughout next year,” he said in a statement on his website. “With deep gratitude and a still strong commitment to a winning path forward for all, I am withdrawing from the race for U.S. Senate.”

The Boston Globe reported that Conroy endorsed Warren in a news conference.

Warren, a Harvard Law School professor, now faces three non-credible candidates and may avoid a primary all together. If her opponents don’t meet a 15 percent threshold of support at the state Democratic convention next year, she won’t face anyone on the ballot in the Sept. 6 primary.

John Walsh, the chairman of the state Democratic Party, called Conroy “hard-working and substantive, a rising talent to watch,” in a tweet. “Classy withdrawal,” Walsh wrote on Twitter.

The race between Warren and Brown has already become heated, with millions of dollars of advertising on TV and sharp accusations between their camps. In one recent poll, Warren had a small edge in a horserace matchup.

Roll Call Politics rates the Massachusetts Senate race a Tossup.