Given four choices, 52 per cent of Democratic caucus-goers said the most important personal quality was that a candidate 'can bring about needed change,' and Mr Obama was the first choice of half of them, according to the caucus entrance polling for reporters and television networks.

Hillary Rodham Clinton won half of those who said it was most important that a candidate 'has the right experience,' but only one in five said that.

John Edwards won almost as large a portion, 44 per cent, of those who said the top priority is that a candidate 'cares about people like me,' but again only one in five chose that attribute.

Only 8 per cent said it is most important that a candidate 'has the best chance to win in November,' and Edwards fared best among them with 36 per cent support.

More than one in five Democratic caucus-goers were under age 30, about twice as many as typically vote in early presidential nomination events.

Fifty-seven per cent of them expressed initial preference for Obama.

Only 10 per cent of those younger voters backed Clinton, and 14 per cent preferred Edwards.

Mrs Clinton won 45 per cent of voters 65 or older, who made up one-fifth of the Democratic electorate.

That was double the share of older people in Iowa's general population.

Nearly six in 10 Democratic voters were attending their first caucuses, and 41 per cent of those backed Obama.

Mr Edwards, who finished second in the 2004 Iowa caucuses, edged out Clinton and Obama among those who have caucused before.

Mr Obama also edged out Clinton, vying to become the first female president, among female voters.

The survey explained how Edwards edged out Clinton for second place under the Democrats' quirky caucus rules.

After an initial vote, supporters of candidates who do not get 15 per cent backing in any caucus site can switch to one of the 'viable' candidates who have cleared that threshold.

The entrance poll found that among supporters of candidates who finished in single digits statewide, only 11 per cent said Mrs Clinton would be their second choice; 31 per cent chose Edwards and 34 per cent Obama.

In the Republican contest, born-again or evangelical Christians comprised six in 10 Republican caucus-goers, and 46 per cent of them favored Huckabee.

Only 19 per cent favored Mitt Romney, a Mormon who has been viewed skeptically by some religious conservatives.

More than one-third of Republican caucus-goers said it matters a great deal to them that a candidate share their religious beliefs, and 56 per cent of that section of the electorate backed Mr Huckabee versus only 11 per cent for Romney.

Given a choice among four personal attributes, 45 per cent of Republican caucus-goers said it was most important that a candidate 'shares my values,' and nearly half of those supported Mr Huckabee.

One-third said it was most important that a candidate 'says what he believes'; Mr Huckabee won among 33 per cent of them, 21 per cent supported Fred Thompson, and Sen. John McCain, Romney and Rep. Ron Paul each won about 15 per cent.

Mr McCain and Mr Romney each won a little more than one-third of voters who said the top priority was that a candidate 'has the right experience.'

Only 7 per cent said the most important attribute was a candidate's electability, and half of those backed Mr Romney.

Iowa caucus-goers typically are more ideological than most other states with competitive presidential nomination contests.

Almost nine in 10 Republican caucus-goers called themselves politically conservative, including 45 per cent who said they are very conservative.

That group went relatively strongly for Thompson.

Among Democratic caucus-goers 54 per cent said they are liberal, and Mr Obama did better among liberals than among more moderate caucus-goers. -- AP