By Kevin Murphy

KANSAS CITY, Missouri (Reuters) - Todd Akin, the Republican candidate in the closely watched U.S. Senate race in Missouri, released a new advertisement on Thursday featuring a woman who says she was raped and had an abortion but supports Akin's anti-abortion stand.

The TV commercial comes in the closing days of a campaign that has drawn national attention because of Akin's remark in August that women's bodies could ward off pregnancy in cases of "legitimate rape."

Akin, a six-term U.S. congressman from the St. Louis area, was heavily criticized by Democrats and lost support from some leading Republicans because of his remark.

A poll by Mason-Dixon Polling & Research released five days ago showed Akin trailing incumbent Democratic Senator Claire McCaskill by just 2 percentage points. He also has regained some of his Republican backing as the party tries to wrest control of the U.S. Senate from the Democrats in Tuesday's election.

The new ad features a woman named Kelly who says she is a full-time student and plans to vote for Akin, who opposes abortion even in cases of rape.

"I'm a woman who's had an abortion. I've been raped in the past," the woman says. "The reason I'm voting for Todd and that I'm so proud of him is because he defends the unborn."

The woman does not say whether she aborted a pregnancy caused by rape. A spokesman for the Akin campaign did not return a telephone call seeking clarification.

McCaskill, who supports abortion rights, has made an issue of Akin's "legitimate rape" comment in some of her commercials.

On Thursday, she released an ad reminding voters that Republican presidential challenger Mitt Romney and some former Republican senators from Missouri denounced Akin's rape comments.

(Editing by James B. Kelleher and Will Dunham)