DENVER (AP)- Fresh off his historic nominating convention, Democrat Barack Obama is embarking on what likely will be the most important 67 days of his campaign for the White House. Republican John McCain was looking to upstage his rival with the announcement of his running mate Friday.

Obama leaves the convention city of Denver as the first black man to be nominated for president by a major political party.

The 47-year-old Illinois senator won over the party faithful - even some die-hard backers of Sen. Hillary Rodham Clinton - but the broader electorate awaits.

His first stop: the battleground states of the Midwest. On Friday, Obama flies to Pittsburgh, where he and running mate Joe Biden will kick off a bus tour of Pennsylvania, Ohio and Michigan.

The goal is to maintain the buzz of a convention that culminated Thursday night with Obama addressing an energetic, flag-waving crowd of 84,000 packed into Denver’s pro football stadium.

"Change happens because the American people demand it - because they rise up and insist on new ideas and new leadership, a new politics for a new time,” Obama told the adoring crowd at Invesco Field.

"America, this is one of those moments.”

McCain, who marks his 72nd birthday on Friday, was determined to create his own gift - by stealing some of the spotlight from Obama with his choice for vice president.

Speculation centered on Alaska Gov. Sarah Palin as two who had been considered top prospects - Minnesota Gov. Tim Pawlenty and former Massachusetts Gov. Mitt Romney - appeared to be out of the running.

Pawlenty said as much on a radio show Friday, and Romney’s associates told The Associated Press he had not been contacted by the McCain campaign.

A GOP strategist close to the McCain campaign said all indications pointed to Palin, 44, a self-styled "hockey mom” and political reformer.

The source spoke on condition of anonymity because he’s not authorized by the McCain camp to speak for the campaign. There was no confirmation from McCain or his advisers.

McCain and his No. 2 are expected to appear together for the first time at one or more rallies planned for Ohio, Pennsylvania and Missouri in the run-up to the Republican National Convention, which starts Monday in St. Paul, Minn.
In the jam-packed football stadium, Obama promised an end to eight years of "broken politics in Washington and the failed policies of George W. Bush” and argued that McCain "doesn’t get it.”

Polls show a tight race between Obama and McCain, with some two months before the election and three high-stakes debates.

"What the people heard ... people of every creed and color, from every walk of life - is that in America, our destiny is inextricably linked. That together, our dreams can be one,” Obama said. Scattered around the stadium, some wept when Obama entered.

"I’m crying because I was around when Martin Luther King died and when John F. Kennedy died, and it’s a long time since then and a long time to get back the dream,” said Francino Norman of Miami.

"This is history. I will tell my grandchildren about this.”

Obama criticized McCain’s support for the war in Iraq, while invoking Franklin Roosevelt and John F. Kennedy as proof that Democrats could be strong on defense.

"If John McCain wants to have a debate about who has the temperament and judgment to serve as the next commander in chief, that’s a debate I’m ready to have,” Obama said.

"John McCain likes to say that he’ll follow bin Laden to the gates of hell - but he won’t even go to the cave where he lives.”

In response, McCain’s campaign said, "Tonight, Americans witnessed a misleading speech that was so fundamentally at odds with the meager record of Barack Obama.”

The Obama campaign emphasized the next phase of the campaign by encouraging supporters in the stadium to use their cell phones to send text messages to friends and to call thousands of unregistered voters from lists developed by the campaign.

Obama’s campaign has identified 55 million voting age Americans across the country who are not registered to vote.

Obama entered the Democratic convention still needing to win over many of Clinton’s supporters. Some Clinton delegates arrived in Denver wary of Obama, still sore over their epic nominating battle.

Obama’s speech followed two days of full-throated endorsements by his one-time rival and her husband, the former president.

Hillary Rodham Clinton issued a short statement Thursday night praising Obama’s speech.

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