Mitt Romney narrowly edged Rick Santorum in Ohio, the biggest prize of Super Tuesday, splitting the Republican electorate along now familiar ideological and religious lines.

Upscale voters: Romney’s competitive showing in Ohio is due in part to increased turnout among wealthier voters. About three in 10 voters had family income of $100,000 or more with nearly half picking Romney. Rick Santorum runs ahead of Romney among voters with incomes below $100,000 and those without a college degree.

Base voters: Romney edges out Santorum among self-identified Republicans in Ohio. Santorum tops Romney narrowly among independent voters, with Ron Paul picking up nearly two in 10. Romney and Santorum within six points among conservatives, but with internal divisions; Santorum has a wide margin among the “very conservative” and Romney pushes back among “somewhat conservative” voters.

Electability: Romney holds a nearly two to one advantage over Santorum among the roughly four in 10 voters who say beating Obama is the most important candidate attribute. This has been Romney’s sweet spot in virtually every contest so far. Santorum locks in voters who are looking for a candidate with strong moral character or is a “true conservative,” winning that group by better than three to one.

Michigan mischief continued? Santorum solidly beats Romney among the small number of self-identified Democrats who turned out, forming an odd coalition with social conservatives. The same phenomenon occured last week in Michigan, when some Democrats crashed the Republican primary to vote for Santorum, thinking he would fare worse against Obama in a general election.

These are preliminary results of a poll of 2,728 Republican voters as they exited primary voting places in Ohio on March 6, 2012. The poll was conducted by Edison Media Research for the National Election Pool, The Washington Post and other media organizations. Typical characteristics have a margin of sampling error of plus or minus three percentage points. The margin of error is higher for subgroups.

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