"They come from a background that is the whole loaf or nothing. They don't compromise and they know how to go if somebody is not with them 100 percent," he said.
But Clinton would solve McCain's problem on this score.
"If Clinton gets the nomination then conservative evangelicals will come out for vote for McCain like he's the second coming," said David Domke, a professor of communication at the University of Washington.
Those white evangelicals already in the Democratic fold in the South though show a decided preference for Clinton. Exit polls for the primary vote on Feb. 5 showed Clinton overwhelmingly won over Tennessee's white evangelical Democrats with 78 percent to only 12 percent for Obama.
YOUNG EVANGELICALS
Analysts see Obama wooing some wavering evangelicals especially young ones by his activism in areas such as the global AIDS pandemic as well as his youthful, rock star image.
"If Obama is the nominee I think he will have an ability to appeal to some of the more moderate evangelicals and there will be a generational factor as well," said Hertzke.
He said while younger evangelicals also tended to be conservative and oppose abortion rights - which Obama supports - they also had a broad range of concerns such as human rights abroad, global poverty and the environment.
The 71-year-old McCain would be the oldest American ever elected to a first presidential term while Obama would be the country's first black president.
Both tales have a wide resonance and Obama and McCain each has a compelling narrative to add that evangelicals find especially attractive: the adult convert and the war hero.
"Obama is comfortable speaking about his faith and he had an adult conversion experience and that has real resonance in the evangelical world," said Hertzke.
McCain by contrast does not seem as relaxed talking about his faith as Obama, who pointedly devotes a whole section to it on his campaign web site.
But patriotic US Christians, who regard sacrifice for "God and country" as a virtue, are impressed by McCain's record as a naval aviator and prisoner of war during the Vietnam War.
And McCain has two trump cards over the Democrats with most evangelicals: his staunch opposition to abortion rights and his unflinching backing of the Iraq war, which many conservative Christians still strongly support.
