Tea Party exponent John Koster is the third Republican congress candidate to express controversial views on rape and abortion during the electoral campaign, with the result of possibly increasing Democrats' chances to hold the White House for other four years.

At a camping fundraising event in the Puget Sound city of Everett, Koster, a Republican congressional candidate for the state of Washington, said that "the rape thing" is not a good reason for a woman to abort.

"Incest is so rare, I mean, it's so rare," Koster told an activist of liberal group Fuse, who had asked him if abortion was acceptable in some situations, "but on the rape thing, it's like ... how does putting more violence onto a woman's body and taking the life of an innocent child that's a consequence of this crime, how does that make it better?"

The activist recorded the conversation that was later released by Fuse.

"When a mother's life is in danger ... I'm not going to make that decision. But the rape thing, you know, I know a woman who was raped and kept her child, gave it up for adoption. She doesn't regret it. In fact, she is a big pro-life proponent," Koster is heard saying.

Koster's remarks were severely criticised by his congressional race opponent Democratic Suzan DelBene,

"Dismissing it as a 'thing' is an awfully casual way for him to talk about it, and I think it highlights how little he understands the ramifications and the seriousness of the issue. So that's very problematic," a spokesperson for DelBene told TPM.

"And the way he approaches the issue and the policy conclusions he comes to, it just highlights the serious problem we have when politicians are trying to dictate women's health care decisions," he said.

Republican congressional candidates' controversial comments on rape and abortion have been the leitmotif - for the Democrats - of the presidential campaign.

Koster is the third Republican to embarrass presidential candidate Mitt Romney with provocative comments regarding rape and abortion which play badly among women voters.

Earlier in October Indiana Senate candidate Richard Mourdock said pregnancy from rape was "something that God intended to happen," causing Romney's staff to publicly distance him from the Tea Party member.

In August it was six-term congressman Todd Akin's turn to trigger outrage with his comments on what he called pregnancy from "legitimate rape."

Romney, who said he opposes abortion except in cases of rape or incest or where it is necessary to save the mother's life, distanced himself from Mourdock.

According to a recent poll by Gallup, Obama is ahead of Romney by eight points among women voters.

Republican presidential candidate and former Massachusetts Governor Romney holds campaign brochure during campaign stop at Alpha Graphics in Hartford (Reuters)