Washington - John McCain's choice of Alaska Governor Sarah Palin may come as a surprise, but she brings strong conservative credentials to the ticket that sorely needs to garner the enthusiasm of the Republican right.

The 44-year-old newcomer to the political scene could quell concerns within a Republican base skeptical of McCain's moderate positions on domestic issues and his history of clashing with the religious right leaders.

McCain was expected to officially announce Palin as his running mate at a rally in Dayton, Ohio on Friday.

McCain has solidly voted against abortion, but has not vocally championed the cause. With Palin, McCain has enlisted someone who is an outspoken, staunchly pro-life candidate who opposes gay marriage and backs other traditional Republican causes.

She's a member of the National Rifle Association, the powerful group that lobbies against regulating access to guns. As governor, she brings executive experience to the presidential bid.

Many political pundits and observers had argued that McCain needed to seek out a conservative to tilt the ticket to the right or risk some Republicans staying home on election day November 4.

Palin could also bring in some support from women who remain disgruntled over Hillary Clinton's defeat and have been slow to embrace Democratic presidential nominee Barack Obama. But that impact remains to be seen.

Palin became the first female governor of Alaska after winning the 2006 election by campaigning on the need to clean up government and by going after the ethical behaviour of the state's Republican leaders.

She defeated incumbent governor Frank Murkowski in the Republican primary before knocking off her Democratic opponent to take charge of Alaska.

Palin's pursuit of ethical issues fits nicely with McCain, 72, who has fought for reform in government since becoming embroiled in a finance scandal in the 1980s. McCain also championed a law to reform campaign finance.

Palin was born in Idaho and her family moved to Alaska when she was an infant. She was the first governor of Alaska to be born after the sparsely-populated state joined the United States in 1959.

Palin began her political career as a member of the Wasilla City Council in 1992, eventually becoming mayor to the town and quickly rising as a statewide figure. She unsuccessfully ran for lieutenant governor in 2002.

Palin was appointed in 2004 to the post of ethics commissioner of the Alaska Oil and Gas Conservation Commission, but later resigned, complaining of the lack of ethics in the commission.

In high school she played basketball and was known as "Sarah Barracuda" for her fierce style of play.

Palin is married to Todd and they have five children. Her oldest son, Track, is a soldier in the US Army and is scheduled for deployment to Iraq in September.

Palin graduated from the University of Idaho with a bachelor's degree in journalism.