US Republican presidential candidate John McCain has a "Religious Right" problem. His likely Democratic rival, Barack Obama, has a Rev Wright problem.
In a country where high levels of belief and church attendance often translate into a major role for religion in politics, analysts say faith may well be a poisoned chalice for the likely contenders in the November White House race.
The faith problem for Obama, who would be the first black president and is within striking distance of the Democratic nomination, stems from voter anger over anti-American sermons by his former pastor the Rev Jeremiah Wright.
Wright has said the September 11 attacks were retribution for US foreign policy and the US Government had a hand in spreading Aids to harm blacks.
Obama has severed ties with Wright but opinion polls persistently show the relationship matters to some voters.
McCain's trouble lies with the Republican Party's conservative evangelical base, the so-called Religious Right, which rallied behind President George W Bush but has been less than enthusiastic about McCain because of his past support for stem-cell research and his failure to back a federal ban on gay marriage.
"The religious right challenge to McCain is far more significant and problematic for his candidacy than the Rev Wright problem for Obama. The reason is because religiously committed Christians are fundamental to a Republican winning the White House," said Michael Lindsay, a political sociologist at Rice University in Houston and a noted expert on faith and politics.
"That is not the case for Democratic candidates, in fact quite the opposite. The so-called secularist wing of American politics is part of the core of Democratic support and especially Obama support," he said.
But that does not mean Obama can exorcise the ghost of Wright, and Lindsay said it could haunt him in swing states - those states that often switch from one party to the other and where the margin of victory in presidential elections is often narrow.
"I think the Wright controversy will continue to plague Obama's candidacy in swing states where religious voters can make a difference like Missouri, Ohio and Pennsylvania."
Polls of voters taken after Tuesday's Kentucky Democratic primary, which Hillary Clinton won easily in what many see as one of her last stands, showed that more than 50 per cent of those who voted thought Obama shared Wright's views.
