By Kevin Murphy
KANSAS CITY, Missouri (Reuters) - Democratic Missouri Senator Claire McCaskill holds a slim lead of 2 percentage points over Republican challenger Todd Akin - essentially a deadlock - in a race being closely watched following Akin's controversial comments on "legitimate rape," a poll released on Saturday showed.
McCaskill had been seen as one of the most vulnerable incumbent Democrats but has led Akin in most polls since he said in August that women could biologically defend themselves against pregnancy caused by "legitimate rape."
Akin said later he misspoke when he made the remark, which led to widespread rebukes even from within his own party, but the six-term member of the U.S. House resisted calls to step aside.
McCaskill led Akin by 45 percent to 43 percent, within the 4-point margin of error for the survey of 625 registered voters conducted from Tuesday through Thursday by Mason-Dixon Polling & Research.
The poll showed 8 percent undecided and 4 percent backing Libertarian candidate Jonathan Dine.
Mason-Dixon conducted the survey for the Kansas City Star, St. Louis Post-Dispatch and St. Louis-based KMOV-TV. The respondents were interviewed by phone and all indicated they were likely to vote in the November 6 general election.
The Akin campaign cited the poll in a statement on Saturday that called the race "a statistical dead heat." McCaskill's campaign said its own tracking survey reflected a 53 percent to 39 percent lead for the incumbent senator.
McCaskill had a strong edge among women in the Mason-Dixon poll, at 47 percent to 38 percent. Men favored Akin in the poll by 48 percent to 43 percent. The margin of error is higher for the gender grouping, Mason-Dixon said.
McCaskill was expected to face an uphill battle for re-election in Missouri, which has become more Republican in recent years. The poll showed Republican Mitt Romney with a large lead in Missouri over President Barack Obama. Respondents favored Romney by 54 percent to 41 percent for Obama.
Republicans need a net gain of four seats in the 100-member U.S. Senate to take the majority from Democrats.
(Editing by Colleen Jenkins)