Governor Deval Patrick announced his endorsement of Senate candidate Elizabeth Warren this afternoon, trying to boost his fellow Democrat as she faces relentless questioning and criticism over her claims to Native American heritage.

Patrick delivered his backing during a joint appearance with the Harvard Law School professor in her Somerville headquarters. Beforehand, the governor wrote in an e-mail to supporters that Warren shares his values of “governing with a view toward our generational responsibility and the politics of conviction as our compass.”

“The reality is that her Republican opponent has made very different choices,” he added. “Time and time again—whether through his votes against summer jobs for our youth, against ending billions of dollars in subsidies to oil and gas companies, or allowing student loan interest rates to increase—Scott Brown has shown he is willing to put the politics of convenience ahead of the people of Massachusetts.”

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Warren is heading into the state Democratic convention this Saturday. She has one remaining primary opponent, North Shore immigration attorney Marisa DeFranco.

Patrick and Warren share a chief political adviser, Doug Rubin. Polls have shown the governor is the state’s most popular politician, recently overtaking Brown, the Republican incumbent senator who Warren is trying to unseat.

Nonetheless, Patrick said in March 2011 that he would wait for the party to select a nominee before endorsing any Democrat. At the time, there was a large field of prospective candidates.

“I’m not picking one. I’m going to support the Democratic nominee,” he told reporters then.

Republicans today accused him of hypocrisy.

“It is a sign of deep panic and desperation in the Warren campaign that Governor Patrick was trotted out today to break his word and endorse her in advance of the Democratic convention,” Nate Little, executive director of the party, said in a statement.

Patrick is in his second term and has said he will not seek reelection. He has been increasingly active in national Democratic politics as a top surrogate for President Obama’s reelection campaign, but had thus far stayed out of the Massachusetts Democratic primary.

Earlier today, Brown appeared in South Boston and announced the support of over 300 veterans in a “Veterans for Brown” coalition. It is led by Tom Kelley, a Vietnam War veteran and Medal of Honor recipient who was forced out of the top veterans affairs position in the Patrick administration.