Washington Introducing Sen. Barack Obama at a rally in Detroit on Sunday, his running mate did not hold back.
"John McCain said he'd follow Osama bin Laden to the gates of hell," said Sen. Joe Biden. "Well, let me tell you something: President Barack Obama will follow him to where he lives and then send him to hell."
Biden's latest ad-lib drew laughter and cheers from the crowd, but there has been a downside to the Democratic vice presidential nominee's freewheeling style: a string of comments that either don't reflect campaign positions or misstate basic facts.
Unlike his Republican counterpart, Alaska Gov. Sarah Palin, Biden has not been shy about talking to reporters, but comments he has made since Obama chose him last month have presented Democrats with their own problems and revived the longtime senator's reputation for gaffes.
In an interview with CBS News that aired last week, Biden described how Franklin D. Roosevelt had appeared before the country on television in 1929 to explain the stock market crash. But Herbert Hoover was president in 1929, and televisions sets did not start appearing in American homes until a decade later.
The next day, confronted with a interview in which Biden had said he opposed the bailout of the insurance company American International Group, a move that Obama supported, the Democratic nominee said that "I think Joe should have waited" before commenting.
And Obama aides spent much of the week defending the candidate's backing of the construction of "clean coal" plants, after a video surfaced on the Internet that showed Biden at a campaign event saying he opposed clean coal. The coal industry is a major employer in Ohio and Pennsylvania, two key swing states where Biden is doing much of his campaigning, and Obama has pledged support for coal plants that emit less carbon dioxide than traditional plants.
The McCain campaign has jumped on the remarks to attack Obama, and the Republican National Committee has started a "Joe Biden Gaffe Clock" that includes dates and video of the senator's comments, which also have included repeated references to brigades of soldiers as "battalions."
"If this race is close, any mistake can be really exploited," said Dan Bartlett, a former top adviser to President Bush who is supporting McCain. "He has this unique capability for someone who is so smart on the issues making these mistakes."
David Wade, Biden's spokesman, defended his boss' "straight talk," adding: "Unlike other campaigns that sequester running mates, we'll proudly continue to unleash Joe Biden to be Joe Biden."
Obama himself has defended Biden, telling NBC last week, "I am very proud of the choice that I made."
And Dan Pfeiffer, Obama's communications director, rejected any suggestion that Biden's role in the campaign would be reduced or changed, calling him a "huge asset" who was "in the battleground states, dominating the media coverage."
Some Democrats have suggested - as Biden himself did recently - that Sen. Hillary Rodham Clinton would have been a better choice as Obama's running mate, but on the whole the party appears satisfied with him.
Biden has long been known for speaking for too long and making occasionally odd remarks, such as when he declared Obama "the first mainstream African American who is articulate and bright and clean and a nice-looking guy" when Biden launched his White House bid in early 2007. A few months earlier he had spoken of the prevalence of Indian accents in Dunkin' Donuts and 7-Eleven stores.
Initially hailed by the party as someone who would add experience as well as appeal to key voting groups such as Catholics, Biden has drawn little attention in recent weeks, crowded out of the media spotlight first by Palin and now by the financial meltdown.