Low Turnout Highlights Romney Squeeze

By Ronald Brownstein // February 8, 2012 | 8:24 a.m.

Republican presidential candidate, former Massachusetts Gov. Mitt Romney pauses while speaking at his Colorado caucus night rally in Denver, Tuesday, Feb. 7, 2012. (AP Photo/Gerald Herbert) (AP Photo/Gerald Herbert)

Rick Santorum's clean sweep of Tuesday's lightly-attended GOP contests underscored front-runner Mitt Romney's continuing struggles with the Republican base, even as recent national surveys show the former Massachusetts governor's standing eroding among independents.

Although exit polls were not conducted Tuesday night, the three states that Santorum swept -- Minnesota, Colorado and Missouri -- are all places where social conservatives represent a central component of the Republican electorate. And in all three states, one of the most striking aspects of Tuesday's results was the sharp decline in the number of people who came out to vote for Romney, compared to four years ago.