As we inch closer to Super Tuesday, expect to see more polling from the main battleground in Ohio.  Newt Gingrich has a wide lead in Georgia, which will assign the most delegates in the 10-state melee, but nowhere else, so the rest of the field will look elsewhere.  Rick Santorum doubles up Mitt Romney in Oklahoma, although the last poll comes from before the last debate, where Santorum had a difficult night, and before the losses in Michigan and Arizona.  RCP has no polling data from Tennessee, and Santorum doesn’t have a full slate of delegates in that state anyway.

The biggest prize after Georgia is Ohio, and Romney wants to deprive Santorum of a victory there to choke off his toughest competitor.  According to a new Marist/NBC poll, he’s climbed to within the margin of error, and leads among early voters:

Rick Santorum and Mitt Romney are locked in a tight battle in the race for the Republican nomination in Ohio.  Among likely Republican primary voters including those who are undecided yet leaning toward a candidate, early voters, and those who voted absentee in the state, Santorum receives 34% to 32% for Romney. …

Key points:

• Among early voters, Romney receives 39% to 35% for Santorum.
• Santorum does the best among likely Republican primary voters who are very conservative — 51% — those who are Evangelical Christians — 44% — and among Tea Party supporters — 41%.
• Santorum — 53% — also does well among values voters.
• Among Republicans, Santorum has 36% to 33% for Romney.  Independent voters divide with 31% for Santorum and 30% for Romney.
• Romney — 37% — does better among likely Republican primary voters who are liberal or moderate compared with 20% for Santorum.  Among likely Republican primary voters in Ohio who are not Tea Party supporters, Romney leads Santorum 36% to 27%.
• Romney also has the advantage among those who want a candidate who can defeat President Obama — 45%.  Among those who emphasize experience, 40% are for Romney.
• Likely Republican primary voters who want a candidate who is closest to them on the issues divide.  Here, Santorum and Romney each has 29%, Paul follows with 24%, and Gingrich has 12%.

This sample consists of 820 likely GOP primary voters from a responder base of 3,566 adults, a fairly significant sample. I could not find the split between Republicans and non-Republicans in the data.  However, the split among both groups favors Santorum in both, 36/33 among Republicans and 31/30 among non-Republicans (as noted above), which leads me to think that the percentage of non-Republicans is probably relatively small.

The other internals produce some surprising results.  Despite the media analysts’ claims, Santorum has no gender-gap problem in Ohio; he beats Romney by four, 36/32, while tying Romney among men 32/32.  The two income demos are almost exactly dead heats, with Romney winning those making $75K or more by one (35/34) and Santorum winning those earning less than $75K by one (33/32). Santorum narrowly wins those 45 years of age and older (36/33) and has a one-point edge among those younger than 45 (31/30).  Those issues are not going to decide the outcome of this primary.

The big difference is among those who vote based on their values or on the perception of candidate strength.  Santorum wins a majority among the former, 53/17 over Romney, while Romney wins by a large margin among those who want to pick someone who can beat Barack Obama, 45/28, and among those who are concerned about having the experience to govern, 40/20.  However, voters are narrowly split on this question:

• Shares values: 28%
• Closest on issues: 25%
• Beat Obama: 29%
• Experience to govern: 16%

Since the “issues” question is a tie, the big dividing lines appear to slightly favor Romney as the primary gets closer.  The issue of candidate strength might be even more of a factor after last week’s sweep for Romney (which includes the caucuses in Wyoming and Washington).  Either way, it looks as though Ohio may be a nailbiter to the end — but if that’s the case, then Santorum’s delegate problems become a big issue.  He needs a win large enough to overcome that handicap, and so far it doesn’t look very likely.  And in a race this close, an early-voting lead — even a thin one —  may be decisive.