WASHINGTON -- Mitt Romney drew strength from Republican loyalists and all but the most conservative voters on Tuesday to claim victory in a grueling GOP presidential primary in his native state of Michigan, an exit poll of voters showed.
Rick Santorum was bolstered by the most ardent conservatives and people whose political views are strongly colored by their religious beliefs, the survey showed. But with Michigan viewed as a solid opportunity for the former Pennsylvania senator to weaken Romney's candidacy, Santorum failed to win more than a modest margin among blue-collar voters – those without college degrees – despite wooing them with populist, made-in-America fervor and his grandfather's coal miner roots.
Romney, the former Massachusetts governor, also cruised to an easy victory in Arizona's GOP presidential contest by winning across nearly all categories of age, income, education and ideology, exit poll results showed there.
In both states, the economy was the dominant issue on voters' minds, as it has been in every state to vote so far. And as he has in every state where voters have been surveyed but South Carolina, Romney triumphed decisively among people who named the economy as their chief concern.
Six in 10 Michigan voters Tuesday were Republicans, with the rest allowed to vote under rules opening the party's primary to others as well. Among those Republicans, Romney prevailed over Santorum, 48 percent to 37 percent.
About 1 in 10 Michigan voters were Democrats and they backed Santorum, a former Pennsylvania senator, by about a 3-1 margin. During the Michigan campaign, Romney accused Santorum of using automated telephone calls to attract Democrats to his candidacy, which Santorum answered by saying Romney had sought independent support in earlier state contests.
The two men ran about neck-and-neck among independents.
In another indication of Romney's hold on committed Republicans, more than 6 in 10 Michigan voters said they would back the GOP nominee no matter what – and Romney bested Santorum among this group, 50 percent to 36 percent.
Santorum won by 14 percentage points among Michigan voters who consider themselves very conservative and by 18 percentage points with strong tea party supporters.
He also triumphed easily among born again or evangelical Christians, reflecting his own strongly held religious beliefs, which he repeatedly emphasized on the campaign trail.
Nearly 6 in 10 Michigan voters said it was important that they share religious beliefs with their candidate, and this group backed Santorum over Romney by 15 percentage points. Around a quarter said a religious match with their candidate was very important, and they supported Santorum by 3-1.
When it came to working-class voters – as measured by those without college degrees – the two men ran about evenly, a clear disappointment for Santorum.
Though Romney has been accused of stirring little passion among his supporters, he led Santorum by 14 percentage points among voters who said their vote was motivated by strong backing for their candidate. Around 1 in 6 voters said their support was motivated by a dislike for the other candidates, and this group picked Santorum by more than 2-1.
More than 4 in 10 voters in Michigan said they supported the federal bailout of the auto industry, according to the exit poll. They gave Romney a slight edge, while the half who said they opposed the federal aid were split evenly between Romney and Santorum.
Both men had both said they oppose the 2008 and 2009 influx of government dollars that kept General Motors and Chrysler afloat as they were foundering. The bailout became a top issue in the final days of the Michigan campaign, at a time when the auto industry – the backbone of the state's economy – has revived.
Underscoring Romney's broad appeal in Arizona, he and Santorum essentially split the 4 in 10 voters there who were born again or evangelical Christians.
Given four choices about what they most wanted in a presidential candidate, the largest share in both states said it was most important that a candidate be able to defeat President Barack Obama in November. A majority of voters who felt that way in each state backed Romney on Tuesday.
The surveys of voters in Michigan and Arizona's GOP presidential primaries were conducted for AP and the television networks by Edison Research. This includes preliminary results among 2,200 voters interviewed Tuesday as they left their polling places at 30 randomly selected sites in Michigan, and among 2,535 Arizona voters as they left 30 polling places. Included were 412 who voted early or absentee in Michigan and 601 in Arizona, who were interviewed by landline or cellular telephone from Feb. 20-26.
The Michigan survey has a margin of sampling error of plus or minus 4 percentage points, while the Arizona exit poll had a margin of sampling error of plus or minus 3 percentage points.