John McCain has chosen his vice presidential running mate but his campaign team is keeping the decision secret until he makes the big announcement today, in a bid to steal some of the spotlight away from Barack Obama.

One of the dark horse contenders for the job, 44-year-old Alaska Gov. Sarah Palin, is looking more and more like she could be McCain's choice.

According to reports a private plane arrived in Cincinnati, Ohio from Alaska on Thursday night with a woman and two teenagers among the passengers.

McCain will be making his announcement in nearby Dayton at noon ET.

Meanwhile, earlier in the day it appeared that two more prominent contenders for the vice presidential candidate could be crossed off the list.

Minnesota Gov. Tim Pawlenty had been widely pegged as McCain's choice, but on Friday he appeared to take himself out of the running, saying he would not be in Ohio when McCain made his announcement Friday.

Massachusetts Gov. Mitt Romney, also considered a top contender, gave no indication he was headed to Ohio either, fanning speculation that former Pennsylvania Gov. Tom Ridge or Democrat-turned-independent Connecticut Sen. Joe Lieberman could be the choice.

But the news that Palin may be in Ohio seemed to make her a more likely candidate -- particularly since the McCain camp is looking for ways to bring disaffected Hillary Clinton supporters into the Republican fold.

McCain is expected to appear with his running mate at two or more rallies in Ohio, Pennsylvania and Missouri ahead of the Republican National Convention which begins Monday in St. Paul, Minn.

McCain's announcement of his running mate will come on his 72nd birthday, and one day after his Republican opponent Obama brought 84,000 people to their feet with his powerful message of change.

Obama accepts nomination

During his speech at Denver, Colorado's Invesco Field on Thursday, Obama accepted the Democratic Party's nomination and vowed to live out his "change you can believe in" campaign slogan, if elected.

"Eight is enough," Obama said, vowing to fix the failed policies of incumbent U.S. President George W. Bush.

"We love this country too much to let the next four years look just like the last eight," he told the massive flag-waving crowd. "On November 4th, we must stand up and say -- eight is enough."

Throughout his one-hour speech, Obama linked his opponent McCain to the policies of the Bush administration, saying his rival has voted with Bush 90 per cent of the time on issues such as health care, education, the economy and more.

"Senator McCain likes to talk about judgment, but really, what does it say about your judgment when you think George Bush has been right more than ninety percent of the time?" Obama said. "I don't know about you, but I'm not ready to take a 10 per cent chance on change."

Obama is now looking to capitalize on the momentum of the Democratic National Convention and Thursday night's rock star-like rally. He will travel to Pittsburgh on Friday with running mate Joe Biden to kick off a bus tour of Pennsylvania, Michigan and Ohio.

On Friday night, McCain's team aired a one night only ad congratulating Obama and noting the acceptance speech came on the 45th anniversary of Dr. Martin Luther King's famous "I Have a Dream" speech on the steps of the Lincoln Memorial in Washington.

"Senator Obama, this is truly a good day for America. Too often the achievements of our opponents go unnoticed. So I wanted to stop and say, 'Congratulations,"' McCain said.

For both candidates the sprint for the White House really begins now, 67 days before Americans go to the polls on Nov. 4.

Obama's pledges

Leading up to Thursday's speech, many analysts said the address represented the most important appearance of Obama's career. Obama had to appeal to ordinary Americans and win over die-hard Hillary Clinton supporters still bitter at their candidate's loss.

CTV's Joy Malbon, reporting from Denver, said Obama was trying to show people that a movement is afoot and that he is poised to deliver change for America.

"He said what he needed to say," Malbon told Canada AM. "He personalized his story, he humanized his story. But what he also did was he punched back at all the accusations and criticism that John McCain has been saying -- that he is a celebrity, that he is elitist.

"He said 'look I come from humble beginnings, I know people are hurting out there.' He was relating to the people and he was telling those people that are sitting on the fence 'look, change is coming, I can fix broken politics, don't believe John McCain, believe me.'"

Obama -- making history as the first black man to be nominated as presidential candidate by a major party -- called the coming election a key moment in U.S. politics.

"We meet at one of those defining moments -- a moment when our nation is at war, our economy is in turmoil, and the American promise has been threatened once more," Obama said.

"These challenges are not all of government's making. But the failure to respond is a direct result of broken politics in Washington and the failed policies of George W. Bush."

Obama also hoped to dispel concerns he won't be as tough as Republicans would be on national security issues.

"When John McCain said we could just 'muddle through' in Afghanistan, I argued for more resources and more troops to finish the fight against the terrorists that actually attacked us on 9/11," Obama said. "You know John McCain likes to say he will follow Osama bin Laden to the gates of hell, but he won't even follow him to the cave where he lives.

"We are the party of Roosevelt. We are the party of Kennedy. So don't tell me that Democrats won't defend this country. Don't tell me that Democrats won't keep us safe.

"As commander in chief, I will never hesitate to defend this nation, but I will only send our troops into harm's way with a clear mission and a sacred commitment to give them the equipment they need in battle and the care and benefits they deserve when they come home," he said.

Obama used his big moment to repeat the campaign promises that would define his presidency, focusing on the economy:

A tax cut for 95 per cent of all working families
A tax code that "doesn't reward the lobbyists who wrote it, but the American workers and small businesses who deserve it."
Stopping tax breaks to corporations outsourcing jobs overseas, and giving them to companies that create them in the U.S.
The elimination of capital gains taxes for small businesses and start-ups creating high-wage, high-tech jobs
The end of American dependence on oil from the Middle East within 10 years