White House rivals President Barack Obama and Mitt Romney have both condemned a Republican politician's controversial intervention in the debate about rape and abortion.
But, while Romney scrambled to distance his campaign from his party ally's statement, Obama seized on the gaffe to embarrass his opponent and underline the gap between their positions.
Congressman Todd Akin of Missouri, his party's nominee for the Senate race in his state, triggered outrage when he said a woman's body can block an unwanted pregnancy during what he termed a "legitimate rape".
Akin's claim, which is unsupported by science, has been used in the past by some Christian conservatives to justify their opposition to all abortions, even those in cases of rape, which more US voters support.
Obama acknowledged Romney had distanced himself, but told reporters: "First of all, the views expressed were offensive.
"Rape is rape, and the idea we should be parsing and qualifying and slicing what types of rape we are talking about doesn't make sense to the American people," he said.
"What I think that these comments do underscore is why we should not have a bunch of politicians, a majority of whom are men, making health care decisions on behalf of women," Obama said.
"I think that the underlying notion that we should be making decisions on behalf of women for their health care decisions, for qualifying forcible rape versus non-forcible rape, are broader issues."
Akin's remark clearly angered Romney.
"Congressman Akin's comments on rape are insulting, inexcusable, and, frankly, wrong," Romney told the conservative National Review Online. "Like millions of other Americans, we found them to be offensive."
In his comments, Akin had appeared to suggest that some women falsely allege rape in order to justify abortion, saying: "If it's a legitimate rape, the female body has ways to try to shut that whole thing down."
Romney dismissed this, saying: "I have an entirely different view. What he said is entirely without merit and he should correct it."
Amid a growing backlash, Akin apologised, saying he used "absolutely the wrong word" and that his comments were "a very, very serious error".
"I really just want to apologise to those that I've hurt," Akin said on the Mike Huckabee Show, a syndicated radio program.
But he also suggested he was not going to stand down in his race against Democratic incumbent Senator Claire McCaskill.
"I'm not a quitter. My belief is we're going to take this thing forward by the grace of God to win this race," Akin said.
Despite his condemnation of Akin's outburst, and his pro-choice position during his time as Massachusetts governor notwithstanding, Romney is campaigning on an anti-abortion ticket.
He wants the US Supreme Court, whose members are appointed by the president, to overturn `Roe versus Wade', the landmark 1973 ruling on the issue of abortion.
Romney's vice-presidential running mate, seven-term congressman Paul Ryan, told the conservative Weekly Standard magazine in 2010: "I'm as pro-life as a person gets."