The gap between former Massachusetts Governor Mitt Romney and former Pennsylvania Senator Rick Santorum is only slightly narrower following the latter’s primary wins in Alabama and Mississippi on Tuesday.

The latest Rasmussen Reports national telephone survey of Likely Republican Primary voters shows Romney with 37% of the vote to Santorum’s 28%. Former House Speaker Newt Gingrich picks up 17% support while Texas Congressman Ron Paul grabs 10% of the vote. Three percent (3%) prefer some other candidate and five percent (5%) are undecided. (To see survey question wording, click here.)

Last week, Romney led Santorum by 12 points – 39% to 27%. Two weeks ago, Romney was up by 16.

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The race is also closer in a one-on-one matchup between Romney and Santorum. Romney now leads Santorum 47% to 42% when the other two candidates are removed. Romney led by 11 points last week. Five percent (5%) now prefer some other candidate in this matchup and five percent (5%) are undecided.

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The national survey of 1,000 Likely Republican Primary Voters was conducted on March 15, 2012 by Rasmussen Reports. The margin of sampling error is +/- 3 percentage points with a 95% level of confidence. Field work for all Rasmussen Reports surveys is conducted by Pulse Opinion Research, LLC. See methodology.

Seventy percent (70%) of likely GOP primary voters now expect Romney to be the eventual nominee, down 10 points from last week. Only 17% feel Santorum will win the nomination, but that’s up from 11% in the previous survey.

Forty-eight percent (48%) think Romney would be the strongest candidate to run against President Obama, down slightly from 51% last week, while 22% say the same of Santorum and 17% believe it to be true of Gingrich.

Most (53%) of national GOP primary voters are now certain of how they will vote, but 42% say they still could change their minds. That’s virtually unchanged from a week ago.

Now, 51% of Republican primary voters still think it is more important to choose a candidate who has the best chance of beating Obama, down from 56% last week. Forty-one percent (41%) prefer a candidate who does the best job representing Republican values, up from 37% a week ago. Romney leads Santorum 50% to 20% among those who put electability first. Among those who put the emphasis on GOP values, it’s Santorum 40%, Romney 24%.

Favorability ratings for all four candidates have slipped a bit from last week. Sixty-nine percent (69%) of likely Republican primary voters nationwide share a favorable opinion of Romney. Santorum is viewed favorably by 64%, Gingrich by 53% and Paul by 38%.

Romney is now viewed as the least conservative conservative. Santorum is seen as conservative by 85% of Republican voters, and 73% describe Gingrich that way. Paul is seen as conservative by 57%, while Romney is seen that way by 52%.

Among Very Conservative primary voters, it’s Santorum 41%, Romney 28% and Gingrich 21%. A plurality of voters who say they are Somewhat Conservative prefers Romney over Santorum 46% to 21%.

Santorum now leads Romney 38% to 33% among Tea Party voters, after the two men were tied a week ago. Romney leads Santorum 42% to 23% among those not affiliated with the movement.

Santorum continues to hold a large lead among Evangelical Christian voters, while Romney is well ahead among other Protestants, Catholics and GOP voters of all other faiths.

Additional information from this survey and a full demographic breakdown are available to Platinum Members only.

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