GOP Senate candidate Del. Bob Marshall of Prince William County, second from right, talks during the first of three debates, April 28 in Roanoake, Va. The candidates debated again May 11 in the Hampton Roads area. (Stephanie Klein-Davis/AP)

George Allen’s Republican rivals tried to rattle him Friday night, but their second debate is unlikely to change the former governor’s status as the presumed GOP front-runner in the crucial U.S. Senate race.

A trio of opponents — Bishop E.W. Jackson, Del. Robert G. Marshall (R-Prince William) and tea party activist Jamie Radtke — tried to label Allen a big spender who did not challenge the status quo in his first and only term in the U.S. Senate.

“Now, George Allen, he was part of the problem,’’ Radtke said. “He voted for every single spending bill, adding $3 trillion to the national debt. . . . We can’t continue on this path.”

Marshall also criticized Allen, saying that as governor Allen tried to spend nearly $150 million on transportation improvements to lure Disney for a history theme park. The park was not built.

“I call it corporate welfare. Other people call it economic development,’’ Marshall said to audience laughter.

For the most part, Allen did not respond directly to the criticisms. Instead, he relied on his stump speech, reiterating the need for new energy sources, smaller government and less regulation.

“This election is about setting the course of America’s comeback,’’ he said. “My friends, if you want to see a renaissance of freedom and opportunity, then I respectfully ask for you to help us and join.’’

With just four weeks remaining before the June 12 primary, it becomes increasingly difficult for any other candidate to beat Allen, who has name recognition and millions of dollars in campaign coffers.

A Washington Post poll released this week showed Allen getting 62 percent of the vote among likely GOP primary voters. Marshall was next with 12 percent, and Radtke and Jackson had 5 and 3 percent, respectively.

The winner of the primary will face former governor Timothy M. Kaine, who faces no opposition for the Democratic Senate nomination in a race that is expected to help determine the balance of power in the U.S. Senate. The seat is being vacated by retiring Sen. James Webb (D).

The second debate of the Senate Republican primary, held in a Virginia Beach waterfront hotel, took place on a Friday night before graduations and Mother’s Day weekend, and it was not televised. About 500 attended, and the organizer, the Republican Party of Virginia, streamed the event live.

The hour-long debate focused almost solely on jobs and the economy, with questions about spending, regulations and contracting. Moderator Nicole Riley, state director of the National Federation of Independent Business, moderated a panel comprised of Virginia business owners.

Allen spent most of his time criticizing Kaine for supporting increased spending and chastised him for serving as chairman of the Democratic National Committee. He told the audience that while he froze college tuition as the state’s chief executive, Kaine increased it by 33 percent.

But Allen did take a moment to defend himself, saying he supported a balanced-budget amendment and a line-item veto.

“People talk about my time in the U.S. Senate,’’ he said. “I’ve been working very hard for several years to rein in spending.”

Kaine’s staff repeatedly tweeted during the event, challenging Allen’s statements and reminding followers of his record.

Allen spoke frequently of his endorsements, two of which he received just this week. The American Conservative Union and National Rifle Association backed him, giving him key support on the right as his opponents try to make the case that he is not conservative enough.

Radtke was by far the most aggressive of Allen’s challengers, criticizing him for taking a pay increase during his time in the U.S. Senate and for not embracing the plan of Rep. Paul Ryan (R-Wis.) to reform entitlements.

“We need a mom in the U.S. Senate,’’ she said. “We don’t need a career politician.’’

Marshall stressed his conservative credentials, speaking about passing a bill that paved the way for Virginia’s lawsuit against the federal government on health care and another that allowed voters to decide that marriage should be between a man and a woman. “I have never voted for a tax increase,’’ he said.

He also said he could take on Kaine because he already had done so on a variety of issues, including giving away tolling authority in Northern Virginia to support Metro extension to Dulles International Airport and including stimulus money in the state budget. “I have beaten Tim Kaine,’’ he said.

Jackson, who said he made a pledge not to criticize his opponents, repeatedly made the case for increased freedom and reduced spending.

“When government gets involved in anything, prices go up,’’ he said. “We have to get the federal government out of Virginia’s business.’’

The four agreed on several issues, including the need to repeal the federal health-care bill and spend money smartly on the military — a statement that was greeted by huge applause in the home of the world’s largest naval base.

The first debate was last month in Roanoke. The third debate will be May 25 in Falls Church.