Republican presidential candidate John McCain, left, hugs Alaska Gov. Sarah Palin as the Arizona senator announces her as his vice-presidential running mate on Friday in Dayton, Ohio. (Kiichiro Sato/Associated Press)Aiming to steal some thunder from Barack Obama's Democratic nomination, Republican presidential hopeful John McCain surprised observers by introducing Sarah Palin as his running mate to a raucous reception at a rally in Dayton, Ohio on Friday.

"She's exactly who this country needs to help me fight the same old Washington politics of 'me first and country second,'" he said of the first-term governor of Alaska.

McCain, who coincidentally turned 72 Friday, welcomed Palin, her husband and four of her five children to the stage at the rally.

"To serve as vice president beside such a man would be a privilege of a lifetime, and it's fitting that this trust has been given to me 88 years almost to the day after the women of America first gained the right to vote," Palin told a cheering crowd.

Palin is only the second female vice-presidential candidate from a major party in U.S. history, the first being Democrat Geraldine Ferraro in 1984.

At 44, she is a full generation younger than McCain, whose campaign has been dogged by concerns about his age.

A newcomer to the national scene, the Idaho-born Palin is also three years younger than Obama.

The Obama camp has been campaigning aggressively in Alaska in an attempt to break the traditional Republican hold on the state in the November election.

In a joint statement released Friday, Obama and his running mate, Delaware Senator Joe Biden, congratulated Palin.

"It is yet another encouraging sign that old barriers are falling in our politics," their statement said.

Obama up at the polls

A Gallup poll released Thursday showed Obama had received a bump from the first three days of the Democratic national convention held in Denver, Colo., three days after polls showed him and McCain in a virtual dead heat in the presidential campaign.

But the effects of both his nomination acceptance speech, which drew a viewership of 38 million people across the United States, and the naming of Palin as the Republican vice-presidential candidate, won't be known until Sunday, when the next poll will be released, the CBC's Henry Champ said.

Obama now holds a lead of six points over his McCain among registered voters, 48 per cent to 42 per cent, a gain fuelled largely by conservative Democrats, Friday's Gallup poll suggested.

The Obama campaign was attempting to court moderate and conservative Democrats at the convention, as well as Hillary Clinton supporters aggrieved by the fallout from a drawn out battle for the Democratic nomination.

Clinton, who was left off the Democratic ticket in favour of Biden, released her delegates at the party's convention and urged them to back her former rival.

The McCain campaign's move to recruit Palin could be seen as an attempt to usher disenchanted Clinton Democrats into the Republican fold, said Champ.

"The difference here is that Hillary Clinton is an exceptionally qualified woman, and her supporters believe she was the best candidate for the presidency of the United States," he said.

"They may feel given Ms. Palin's shortness of résumé that it's an affront in this particular case."

Self-styled 'hockey mom'

Palin referred to Clinton favourably in her acceptance, making reference to the 18 million votes she received in the Democratic primaries.

"Hillary left 18 million cracks in the highest, hardest glass ceiling in America," she said.

"But it turns out the women of America aren't finished yet, and we can shatter that glass ceiling once and for all."

First term Alaska Gov. Sarah Palin is seen during a press conference in Anchorage in an Aug. 13, 2008 file photo. (Anchorage Daily News/ Marc Lester/Associated Press)Palin campaigned on ethics reform in the 2006 GOP primary to defeat incumbent Frank Murkowski, who served 22 years in the U.S. Senate before winning the governor's seat in 2002. Prior to her win, Palin was mayor of Wasilla, Alaska, a small town where she had previously served as a councillor.

The Obama campaign, despite congratulating her on her selection, was quick to point out her inexperience.

"Today, John McCain put the former mayor of a town of 9,000 with zero foreign policy experience a heartbeat away from the presidency," Adrianne Marsh, a spokeswoman for Obama, said in a written statement.

But many see McCain's risky choice as a smart one for a party that needs to distance itself from its old image.

A self-styled hockey mom, Palin has the rare distinction being considered both a reformer and right-wing Republican who will appeal to the party's core base, former Republican consultant Jordan Lieberman told CBC news.

"There's a big difference between serving as president with little foreign policy experience and serving as vice president with little foreign policy experience," Lieberman said. "She has plenty of time to grow into the foreign policy role."

"It's an absolutely brilliant choice," said Mathew Staver, dean of Liberty University school of law. "This will absolutely energize McCain's campaign and energize conservatives."

Palin tough on big oil

Palin has a growing reputation for bucking her party's establishment and Alaska's powerful oil industry.

During her first year in office, Palin moved away from the powerful old guard of the state Republican Party and presided over a tax increase on oil company profits that now has the state's treasury swelling.

But she is a proponent of petroleum development, in tune with McCain, although the two disagree on drilling in Alaska's protected Arctic National Wildlife Refuge. She favours drilling there, while he opposes it.

The governor also opposed designating polar bears as threatened under the Endangered Species Act, fearing that step would get in the way of a proposed natural gas pipeline tapping the North Slope's vast reserves.

Socially, she has a strong anti-abortion record that is in line with Republican orthodoxy, whose support McCain needs to prevail in the national campaign.

She opposes gay marriage — constitutionally banned in Alaska before her term as governor — but exercised a veto that essentially granted benefits to gay state employees and their partners.

Palin is a member of the National Rifle Association, and her oldest son, Track, 19, enlisted in the army in 2007 on the sixth anniversary of the Sept. 11 attacks.

McCain wanted Lieberman 'in his heart of hearts'

As top prospects seemed to drop away, speculation moved toward Palin, whose name had come up in the weeks leading up to the Republican National Convention in Minneapolis on Monday.

"I think [McCain] went down a long list and found a problem with everybody, all the bigger names, all the people that people have heard of," Martin Gottlieb, a political columnist for the newspaper Dayton Daily News, told CBC news earlier Friday.

"I think in his heart of hearts he wanted Joe Lieberman, but people told him that would tear the party apart."

Lieberman, a senator from Connecticut who now sits as an independent, was Al Gore's running mate on the 2000 Democratic ticket.

He is a close ally of McCain, but is pro-choice and differs from the Republican rank and file on a number of other issues.

Other names mentioned in the race included:

• Tim Pawlenty, governor of Minnesota.
• Tom Ridge, the former governor of Pennsylvania.
• Mitt Romney, the former governor of Massachusetts.
• Former congressman Rob Portman of Ohio.

With files from the Associated Press