WASHINGTON — Breaking his self-imposed vow of silence, President Bush is wading deeper into the campaign to succeed him, declaring that he is a “strong asset” to Republican hopefuls and castigating Democrats who failed to denounce a MoveOn.org ad that mocked General David Petraeus.

“I thought the ad was disgusting,” Mr. Bush said this morning at a White House press conference, referring to the New York Times display in which MoveOn.org referred to the commander of American forces in Iraq as “General Betray Us.”

“I was disappointed that not more leaders in the Democrat Party spoke out strongly against that kind of ad,” the president said when asked about Democratic candidates who did not rebuke the MoveOn.org ad, accusing them of being more fearful of alienating a left-wing anti-war group than of alienating America’s military.

“That leads me to come to this conclusion: that most Democrats are afraid of irritating a left-wing group like MoveOn.org — or more afraid of irritating them than they are of irritating the United States military.”

Mr. Bush added: “That was a sorry deal. It’s one thing to attack me; it’s another thing to attack somebody like General Petraeus.”

The leading Democratic presidential candidates, Senator Clinton, Senator Obama, and John Edwards, have largely dodged direct questions about the ad while emphasizing that their criticisms of Iraq war policy are aimed at Mr. Bush, not General Petraeus.

The executive director of MoveOn.org’s political action committee, Eli Pariser, responded quickly with a statement saying, “What’s disgusting is that the president has more interest in political attacks than developing an exit strategy to get our troops out of Iraq and end this awful war.”

Early this afternoon, the Senate voted 72-25 in favor of a resolution that said General Petraeus “deserves the full support of the Senate” and that lawmakers “strongly condemn personal attacks on the honor and integrity of General Petraeus and all members of the United States Armed Forces.”

Mrs. Clinton and another Democratic presidential hopeful, Senator Dodd of Connecticut, voted against the symbolic measure, while Mr. Obama and Senator Biden of Delaware did not vote.

Mrs. Clinton’s vote drew an immediate attack from a Republican candidate, Mitt Romney, who issued a statement saying: “The idea that she would be a credible commander-in-chief of our armed forces requires the willing suspension of disbelief.”

There was no immediate response from the Democratic White House hopefuls to the president’s comments this morning.

The party’s national chairman, Howard Dean, responded by accusing Mr. Bush of “spinning the facts to try to sell his failed stay-the-course strategy in Iraq.” He also criticized Republicans for blocking a vote yesterday on a bill requiring longer breaks between overseas deployment for American troops.

The president has repeatedly refused to engage in questions about the presidential race that has been heating up for months, saying he will resist the temptation to be “pundit-in-chief.” But he strayed from that line this morning, offering advice to Republicans and declaring that he would be a “strong asset” rather than a liability, despite his low approval ratings.

“Candidates who go out and say that the United States is vulnerable to attack and we’re going to make sure our professionals have the tools necessary to protect us are going to do well,” he said. “Candidates who go out and say that helping these Iraqis realize the benefits of democracy are going to do well.”

He added that candidates should state “clear principles” on foreign policy and that “candidates who say we’re not going to raise your taxes are going to do well.”

Following decisions by the leading GOP candidates to decline invitations to speak at forums before black and Hispanic audiences, Mr. Bush also pushed them to reach out more to minority communities.

“My advice to whoever will be our nominee is to reach out to the African American community, as well as other communities, because I believe that we’ve got a very strong record when it comes to empowerment, when it comes to education, or home ownership, or small business formation,” he said.