DENVER — Barack Obama's campaign sought Sunday to assure Democrats disgruntled over the fact he didn't pick Hillary Clinton as his running mate, as rival John McCain launched a new ad seeking to aggravate those tensions.
McCain started airing the ad Sunday featuring clips of Clinton criticizing Obama during their long and often heated primary battle for the Democratic presidential nomination.
It then says that Obama deliberately slighted Clinton by passing over her to pick Joe Biden as his vice presidential running mate.
"Who won millions of votes but isn't on the ticket?" the ad says. "Why? For speaking the truth."
Obama's chief strategist, David Axelrod, responded by stressing that Clinton endorsed the Biden pick, apparently hoping that will sway any disgruntled Clinton supporters.
"He felt that Senator Biden would be the best fit for him at this time," Axelrod said on ABC's This Week program.
"And I was pleased that Senator Clinton gave such a robust endorsement to Senator Biden as the nominee yesterday...I think it was a good choice. I think everybody recognizes it."
He also said that Obama respects Clinton and will listen to her advice during the campaign.
"He has a high regard for Senator Clinton. She's going to be an important voice in this campaign. She's going to be an important voice in moving this country forward in the next administration."
A day after Obama unveiled Biden as his pick, delegates started pouring into Denver for Mondays start of the Democratic National Convention.
Obama was heading to Wisconsin for a single campaign event and Biden was back home in Delaware working on the speech he will give accepting the vice presidential nomination.
McCain was at home in Arizona weighing his own running mate choice, which he's likely to unveil next weekend. The Politico Web site reported that McCain has added former Secretary of State Colin Powell to his list of possible picks.
He had no public events scheduled Sunday.
But MSNBC reported that McCain called his Senate colleague Biden and in an interview aired on CBS, McCain praised the selection of Biden.
"I think he's a good selection," McCain said. "Joe and I have been friends for many, many years, and we know each other very well, and so I think [Obama's] made a very wise selection."