(Reuters) - Leading candidates in the race for the November 2008 U.S. presidential election head into a new round of nominating contests in the state-by-state selection process after Republican John McCain won on Saturday in South Carolina and Democrat Hillary Clinton and Republican Mitt Romney won in Nevada.

Following are brief profiles of the main contenders:

DEMOCRATS:

HILLARY CLINTON, 60, beat rival Barack Obama in Nevada, giving her momentum going into the Democrats' South Carolina contest on Saturday, January 26. Clinton, a senator from New York, would be the first female U.S. president if elected. A former first lady, she has emphasized efforts to insure 47 million Americans without health coverage and criticized opponents for lack of experience. After a disappointing third-place finish in Iowa, Clinton bounced back to a surprise win in New Hampshire. Her once strong lead in national opinion polls has narrowed.

JOHN EDWARDS, 54, is focused on winning the Democratic primary in South Carolina, the state where he was born and where he won the primary during his unsuccessful 2004 presidential bid. He finished a distant third in Nevada. The former senator from North Carolina was the Democratic nominee for vice president in 2004. He has made combating poverty a major campaign theme and called his vote to authorize military action in Iraq a mistake. Edwards now urges withdrawal of U.S. troops from Iraq. He edged out Clinton for second place in Iowa but came in third in New Hampshire and trails Obama and Clinton in national polls. His wife, Elizabeth, is being treated for a recurrence of cancer.

BARACK OBAMA, 46, hopes to rebound from his Nevada loss with a win in South Carolina, where a majority of Democratic voters are black. Although Clinton won more votes in Nevada, Obama said because of his strength in some areas outside Las Vegas, he would have support of 13 delegates to Clinton's 12 at August's Democratic nominating convention. Obama, an Illinois senator who would be the first black U.S. president, won the opening contest in Iowa. He gave the keynote address at the 2004 Democratic convention before he was elected to the Senate. He has opposed the Iraq war from the beginning and tried to cast himself as a Washington outsider. He scored a surprise victory in Iowa and came in second to Clinton in New Hampshire.

REPUBLICANS:

RUDY GIULIANI, 63, was once the party's front-runner but is fighting to stay alive in the coming votes. The former New York mayor, who has made his leadership during the September 11 attacks a centrepiece of his candidacy, did not campaign heavily in the states holding the early contests. He focused instead on larger states that vote later, particularly Florida, which holds its primary on January 29. Widely shunned by many conservatives because of his support for abortion rights, gun control and gay rights, he received the endorsement of Christian evangelist Pat Robertson.

MIKE HUCKABEE, 52, narrowly lost to John McCain in South Carolina despite the Baptist minister's hopes to win with support from the state's large bloc of evangelical Christians. The bass-playing former Arkansas governor was born in Hope, Arkansas -- the birthplace of Bill Clinton. He won the Iowa caucus thanks to strong support from fellow evangelicals, who admire his religious beliefs and conservative stances on social issues like abortion and gay marriage. Known for his wit, he has been criticized for a lack of knowledge on foreign policy.