By Steve Holland
BETHEL PARK, Pennsylvania (Reuters) - After years of mistrust, Republican Mitt Romney is slowly beginning to convince reluctant conservatives to unite behind him ahead of the November 6. presidential election.
Using a mixture of public attacks on President Barack Obama's economic record, and quieter lobbying with conservative groups, the former Massachusetts governor is now seeing the fruit of his efforts to shore up his right flank.
U.S. House of Representatives Speaker John Boehner endorsed Romney on Tuesday as the candidate who can "put Americans back to work."
And a new Washington Post-ABC News Poll showed rising support from Republicans for Romney in the wake of conservative favorite Rick Santorum pulling out of the race last week.
A record high of 69 percent of Republicans, including 80 percent of conservatives, hold favorable views of Romney, the poll showed.
Aware of doubts that he is too moderate, the Romney campaign has engaged in behind-the-scenes efforts to get conservatives behind him. One method has been to send a representative to weekly meetings of dozens of conservatives held in Washington by Grover Norquist, who heads Americans for Tax Reform.
"I think they've done a good job," Norquist said of the Romney camp's efforts. "(Conservatives) will come around, but I think it's probably wise of them to do what they appear to be doing and that is reaching out and asking. People like to be asked."
In addition, the Romney campaign has been making calls to conservative groups, such as the National Association of Marriage, which endorsed him last week.
"Some of it is falling into place without a lot of effort," said a Republican consultant with close ties to the campaign. "He and the staff will be reaching out to these groups, and out in the states, the state leadership is reaching out to the local conservative groups and coalitions that weren't for Romney."
Romney is also emphasizing fiscally prudent, pro-business views on the U.S. economy as a way to answer questions from the party's base on whether he is sufficiently different from Obama.
Some prominent conservative leaders have yet to back Romney, such as Santorum, who reluctantly pulled out of the race last week when faced with the real possibility of losing his home state of Pennsylvania to Romney.
Former Alaska Governor Sarah Palin, a Tea Party favorite, has also been cool to Romney. Former presidential candidate Michelle Bachmann has yet to endorse Romney, but may do so soon.
Holdouts like Richard Viguerie, chairman of ConservativeHQ.com, say they harbor deep doubts about Romney's moderate roots, such as his development of a healthcare plan for Massachusetts that Obama says was a model for the U.S. overhaul conservatives hate.
"There's no reason for us to trust Romney at this point," Viguerie said. "The next move is up to him. He's got not a hill, but a mountain, to climb."
Viguerie said Romney could help himself by naming a reliable conservative to be his vice presidential running mate, such as Louisiana Governor Bobby Jindal and Florida Senator Marco Rubio.
Former Mississippi Governor Haley Barbour, who flirted with a run for the Republican presidential nomination, said Romney can help himself by keeping the focus of his campaign on Obama's record.
"Most conservative Republicans recognize that Romney is not as conservative as they are," Barbour told Reuters. "He's not as conservative as I am. But he is far more conservative than Obama."
"Romney needs to make the election about Obama's policies and the failed results of those polices and compare them to the policies he would pursue," he said. "If he does that, don't get between Tea Party people and the polling place on Election Day."
On a tour of Pennsylvania, Romney is pounding away at this theme, saying the economy is weighed down by Obama's deficit government spending and tighter federal regulations while he wants deep budget cuts and fewer rules on business as a way to trigger job growth.
"This campaign is just getting going," Romney told a Tea Party group in Philadelphia on Monday night. "It's getting fun. And the contrast could not be bigger. He (Obama) said the other day this is going to be a defining election. That's one thing I agree with him on."
(Editing by Cynthia Osterman)