(CNN) - Rick Santorum's lead in Ohio's Republican presidential primary has evaporated, according to a new poll released just four days before what can arguably be considered the most important contest on Super Tuesday.
A Quinnipiac University survey released Friday indicates that 35% of likely GOP primary voters in the Buckeye State say they back the former senator from Pennsylvania, with 31% supporting former Massachusetts Gov. Mitt Romney. Santorum's four-point advantage is within the survey's sampling error, meaning it's basically all tied up in Ohio.
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According to the poll, 17% back former House Speaker Newt Gingrich and 12% support Rep. Ron Paul of Texas. Thirty-four percent of those who are backing a candidate say they may change their minds by Tuesday's primary.
The poll was conducted Wednesday and Thursday, after Romney's big victory in Arizona's primary and after he narrowly edged out Santorum to win his native state of Michigan.
Santorum held a seven-point lead over Romney (36% to 29%) in a Quinnipiac poll released Monday, before the Arizona and Michigan contests.
"At this point, the Buckeye State is too close to call and is clearly a two-man race between Sen. Rick Santorum and Gov. Mitt Romney," said Peter A. Brown, assistant director of the Quinnipiac University Polling Institute. "A third of the electorate say they still might change their mind. With four days until Super Tuesday, they certainly will be exposed to enough negative television ads to provide fodder for those who might want to switch – or switch off."
The survey indicates Santorum slightly ahead of Romney among men (34% to 28%), with 37% of women backing Santorum and 33% supporting Romney. Santorum holds a 13-point lead among self-described conservatives and a 17-point lead among self-described tea party movement members. Romney has a 20-point lead among those who describe themselves as moderates.
Ohio's primary is open, meaning independent voters and Democrats are allowed to cast ballots in the GOP contest. Sixty-three delegates are up for grabs Tuesday in the Buckeye State, which besides being a crucial primary state is also one of the most highly contested battleground states in the general election.
The Quinnipiac University poll was conducted between February 29 and March 1, with 517 likely Republican primary voters in Ohio questioned by telephone. The survey's sampling error is plus or minus 4.3 percentage points.
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