Dave Matthews, Sheryl Crow perform at kickoff concert for Democratic convention

MORRISON, Colo. -- Singing at the Democratic convention, Sheryl Crow dedicated her song "Strong Enough" to Barack Obama and then added a twist to the lyrics for the occasion.

"Are you strong enough to be my man, or my president?" Crow sang to her party's nominee and his newly announced running mate, Delaware Sen. Joseph Biden.

Dave Matthews and Sugarland's Jennifer Nettles also sang at the kickoff concert Sunday night at Red Rocks Amphitheater outside Denver. The national convention began Monday at the Pepsi Center.

"What I'm hearing from Sen. Obama is a lot like what we heard from Robert Kennedy," Crow told the crowd between tunes. "No matter what campaign ad we see or how it's spun, hope is important. It's what this country was based on."

She said beforehand that she hadn't been swayed from speaking out for Obama by the candidate's "celebrity."

"That tag that Sen. Obama's been given is a campaign ploy, obviously, by the Republican party," Crow said. "I don't see him hanging out. I have yet to see him at any celebrity events."

Matthews, playing with Tim Reynolds, was less pointed with his commentary, while Nettles played up the night's theme of environmentalism. Denver's mayor has worked with hotels, restaurants and organizers to make the convention a green event.

"This is the first time that a political convention of any sort has been surrounded with the awareness of environmental issues," Nettles said before playing. "So that feels like it's on the cutting edge."

Her bandmate Kristian Bush said, "Yeah, and regardless of what political affiliation you want to align yourself with, this is an issue. It's real, no matter which side you decide to attack it from."

Aside from the Dixie Chicks, it's rare for a country group to play a high-profile Democratic Party-sponsored event. So are Nettles and Bush Democrats?

"We don't say. We stay away," replied Nettles, laughing. "It's like honey, what do you want to be, a pariah? What do you want to be, crucified? It's a good thing in this country. We don't have to tell anybody. It's no one's business who we vote for."

Among those who showed up at the event organized by well-connected environmental activist Laurie David: Colorado Gov. Bill Ritter, Virginia Gov. Tim Kaine and Robert Kennedy Jr.