Impersonator Gerardo Puisseaux made his best Barack Obama this week while standing in front of a poster depicting the U.S. Capitol outside Denver's Pepsi Center. OBAMA THREAT NOT CREDIBLE, POLICE SAY

Authorities investigating a possible plot to assassinate Barack Obama at the Democratic National Convention have three men in custody -- including one found with high-powered rifles, three fake IDs and two wigs -- but they expressed doubts Tuesday that the suspects posed a credible threat.

The men arrested Sunday face drug and gun counts but are not expected to be charged with making threatening statements or national-security-related crimes, said a federal-law enforcement official in Denver.

One of the men, Nathan Johnson, 32, told a Denver TV station that others involved in the case had made racist statements about Obama and had discussed killing him Thursday, the day of his acceptance speech. When asked whether he felt there was a plot to kill Obama, Johnson said, "I don't want to say yes, but I don't want to say no."

U.S. Attorney Troy Eid said, "We're absolutely confident there is no credible threat."

Three senior FBI officials said it's unclear whether shooters could have had a clear path to hit the stage from outside the convention hall. At least two of the men may have had white supremacist ties, officials said. Also arrested were Shawn Robert Adolf, 33, and Tharin Gartrell, 28.

BIDEN ADMITS HIS PAST FOIBLES

Vice presidential candidate Joe Biden thanked Delaware delegates at a breakfast Tuesday for standing by him and served up a mea culpa for his foibles. He acknowledged that his spot on the ticket will come with challenges. "I didn't always comport myself in the way that I wanted to," he said.

Aides said Biden was referring to his tendencies to shoot from the hip that sometimes gets him in trouble, including calling Obama "articulate" and "clean" and saying "you cannot go to a 7-Eleven or a Dunkin' Donuts unless you have a slight Indian accent."

OBAMA: OSHA RULES SHOULD BE TOUGHER

Obama renewed his emphasis on economic themes Tuesday, pledging to enforce occupational health and safety regulations as president and declaring that rival John McCain "doesn't get it" when it comes to the anxieties that many middle-class workers are facing.

In Missouri, he spoke to workers at a hangar where American Airlines planes are serviced. The plant employed 3,500 people in 2001, but the work force has since been cut to about 1,000.

Obama briefly mentioned the convention, praising his wife, Michelle, who spoke Monday. "She was good. I could not have been more proud of her. And she also looked cute, which didn't hurt."

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