By Ros Krasny
KEENE, New Hampshire (Reuters) - Touting his middle-class roots, Vice President Joe Biden took another swipe at Republican presidential candidate Mitt Romney on Tuesday as he reveled in his role as the president's campaign attack dog.
Biden blasted the presumptive Republican nominee Romney as failing to care about workers at companies acquired by his former investment firm Bain Capital. Romney is slated to face President Barack Obama in the November 6 election.
"Your job as president is to promote the common good. That doesn't mean the private guys are bad guys. They're not. But that no more qualifies you to be president than being a plumber, and by the way, there are a lot of awful smart plumbers," Biden told supporters at Keene State College in New Hampshire.
Biden, who often talks of his boyhood in industrial Scranton, Pennsylvania, has taken the lead in attacking Romney for overseeing workers' jobs losses while he headed private equity firm Bain Capital.
On Tuesday, Biden met firefighters and drank a milkshake at a diner as he toured New Hampshire, one of the crucial "swing" states where the November 6 election is likely to be decided.
Supporters offered cheers of "Get 'em, Joe," and "Kick butt in New Hampshire," as he entered the diner in Peterborough.
Biden has a reputation for speaking out of turn and embarrassed Obama two weeks ago by effectively announcing the administration's support for gay marriage before his boss did.
But he is the White House's favorite point man with blue-collar workers, a crucial role in an election that may be decided by white voters in Rust Belt states with whom Obama has struggled to connect.
Biden made an impassioned speech last week in Ohio where he said former executive Romney "doesn't get" ordinary Americans.
BAIN IS 'FAIR GAME'
Former New Hampshire Governor John Sununu, a top Romney supporter, acknowledged on Tuesday that the Republican's business record is fair game in the battle for the White House. But he accused Obama's campaign of cherry-picking by running ads that only focus on Bain investments that were unsuccessful.
"I think the Bain record as a whole is fair game," Sununu said. "I think what you have to do is an honest evaluation," he told reporters on a conference call before Biden's speech.
He said Bain, which created thousands of jobs by helping found big companies like office supply chain Staples, had a good batting average for a private equity firm.
Biden acknowledged that Romney had performed well as a businessman, but said this did not equip him to govern.
"Making money for your investors, which Romney did very well, is not the president's job. The president has a different job," Biden said.
His speech was well-received by the crowd of hundreds of supporters. "He could resonate with the regular people," said Sylvie McCarthy, a recent Keene State graduate. "One woman next to me was crying. I had to pat her leg."
Debate over Romney's record at Bain in the 1990s - and whether Obama's team should focus so much on it - has taken over the presidential race.
Escalating the rhetoric over Bain, the No. 3 Democrat in the U.S. House of Representatives said Romney was involved in "raping" companies by buying them and breaking them up.
"There's something about raping companies and leaving them in debt and setting up Swiss bank accounts and corporate businesses in the Grand Caymans -- I have a real serious problem with that," Representative James Clyburn said on MSNBC on Tuesday.
Obama weighed in on Monday to defend ads about Bain by his campaign and its allies. He said the spots were justified because Romney has made Bain "his main calling card" to back up his run for president in an election focused on jobs.
Romney co-founded Bain in the early 1980s, but left in 1999 to run the Salt Lake City Olympics and pursue his political career, including a term as governor of Massachusetts. His investments and retirement package have been his main source of income since then.
The Republicans' argument that criticism of Bain is undermining free enterprise were given an unexpected boost on Sunday when the Democratic mayor of Newark, New Jersey, Cory Booker, a prominent Obama supporter, called the Obama campaign attacks over Bain "nauseating."
The general election on November 6 is likely to be close, and job creation is a central theme of campaigning. The contest between Obama and Romney will likely depend on how Americans are feeling about the sluggish economy.
A Washington Post-ABC News poll released on Tuesday had Obama supported by 49 percent of voters, to 46 percent for Romney, a statistical dead heat. They were tied on handling the economy, at 47 percent each.
More than half of all Americans said the economy is their main concern, far more than health care, taxes, the U.S. budget deficit and social issues like gay marriage.
Two weeks after Obama announced he supports gay marriage, an NBC News/Wall Street Journal poll showed Obama's position made about the same share of voters - 17 percent - likely to vote for him, as the 20 percent who said it made them more likely to back Romney. Sixty-two percent said the president's support for gay marriage would not make a difference in their vote.
(Additional reporting by Sam Youngman and Patricia Zengerle in Washington; Writing by Patricia Zengerle; Editing by Alistair Bell and Cynthia Osterman)