Republican presidential nominee John McCain, buoyed by a unifying GOP convention and the spark of running mate Sarah Palin, plunged into a competitive, eight-week struggle with Democrat Barack Obama over which party can best bring change to Washington.

Before a roaring crowd of delegates McCain vowed Thursday night to vanquish the "constant partisan rancor" he said was plaguing the nation as he embarked on an eight-week effort to win the White House.

"I will reach out my hand to anyone to help me get this country moving again," McCain said. Joining him after the speech was Palin, the Alaska governor whose national political debut has helped solidify GOP conservatives behind the party ticket.

McCain and Palin left Minnesota immediately after the Arizona senator's acceptance speech, bound for Democratic-tilting Wisconsin as Obama planned campaign and fundraising events in Pennsylvania and New Jersey.

In a convention speech lasting nearly an hour, McCain promised before a nationwide television audience to govern as a political maverick with a bipartisan bent. And he reminded voters of the 5 1/2 years he spent in a North Vietnamese prison.

"I fell in love with my country when I was a prisoner in someone else's," he said. "I was never the same again. I wasn't my own man anymore. I was my country's."

His speech capped the party convention, but vice presidential nominee Palin was arguably the star, electrifying Republicans Wednesday in a slashing speech against Obama and his running mate, Delaware Sen. Joe Biden. She is the first female running mate in GOP history.

The 72-year-old McCain, campaigning to become the oldest first-term president in history, presented himself as a reformer willing to take on his fellow Republicans, including an unpopular President Bush. He chastised Republicans for falling prey to the temptations of power before voters deprived them of their majorities in the House and Senate two years ago.

"We were elected to change Washington, and we let Washington change us," McCain said. "We lost the trust of the American people when some Republicans gave in to the temptations of corruption."

McCain's speech was largely devoid of the partisan edge that characterized Palin's, which was aimed at solidifying conservative and evangelical voters behind the GOP ticket. Democrats countered that Palin was long on personal attacks and short on remedies for the nation's troubles.

Palin, 44, has been under a media microscope since McCain tapped her last week, but she seems to have energized Republicans heading into the fall campaign. Virtually unknown nationally a week ago, Palin has faced heavy scrutiny, some of it relating to her tenure as mayor of Wasilla, Alaska, and her time as governor, but most involving her 17-year-old, unmarried pregnant daughter.

For the most part, McCain's aides have kept Palin out of public sight while vociferously defending her readiness to become vice president.

"I'm very proud to have introduced our next vice president to the country," McCain said. "But I can't wait until I introduce her to Washington."

Democrats held their own convention last week in Denver, nominating Biden as running mate for Obama, whose own acceptance speech drew an enthusiastic crowd to an outdoor football stadium.

The back-to-back political conventions — outdated as nominee-selection exercises but important infomercials and party-building events — each served their purposes in setting up the fall campaign.

The polls indicate a close race between McCain and Obama, at 47 a generation younger than his Republican opponent, and a slight favorite in a race likely to be decided in typical swing states in the Midwest such as Ohio and in nontraditional targets for Democrats, such as Colorado and Virginia.

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