In Mississippi in particular, Romney struggled to prove that he could make a strong showing in an electorate dominated by the GOP factions that have been the most hostile toward his candidacy.
At least eight in 10 voters in Mississippi and Alabama identified themselves in exit polls as evangelical Christians, a group that has been suspicious of Romney’s Mormon faith and of his past support for abortion rights.
Typically, Republicans anoint their nominee early. But this year has produced the most unpredictable and bitter fight in recent history, one that is pitting the establishment wing of the GOP against the insurgent forces of the tea party and social conservatives.
The races in Mississippi and Alabama picked up intensity after the mixed results of the March 6 Super Tuesday contests, which did not winnow the field as many had expected.
“Most people would have said a month ago it will be over by the time you get to Mississippi and Alabama,” said former senator Trent Lott (R-Miss.), a Romney supporter.
Romney’s supporters had hoped that he could put to rest questions about whether he can win over the party’s base.
Exit polls Tuesday suggested that electability was the foremost concern of voters in the two Southern states, as it had been in many of the earlier primaries. A plurality in both Mississippi and Alabama said the quality that mattered most to them in deciding which candidate to support was whether he can beat Obama.
But Santorum triumphed because just as many voters said that having a “strong moral character” or being a “true conservative” were the most important attributes. He won these voters by big margins.
Some Romney supporters suggested that Republican voters may be growing anxious to see this prolonged nominating contest come to an end, so that the nominee can begin marshaling an organization and financial support for the general-election contest.
“As the race progresses, the drumbeat gets louder and louder to get it over,” said Romney supporter Henry Barbour, a nephew of former Mississippi governor Haley Barbour and a Republican national committeeman.
Romney benefited from the muscle of the Mississippi political establishment. Nearly every Republican official elected statewide lined up behind him, including Gov. Phil Bryant, who gave Romney a late endorsement last week after initially backing the candidacy of Texas Gov. Rick Perry.
Henry Barbour’s younger brother Austin ran much of the Romney campaign’s ground operation in the state, and state auditor Stacey Pickering, who also has a surname famous in Mississippi Republican politics, was chairman of Romney’s campaign there.
Staff researcher Lucy Shackelford and polling manager Peyton Craighill contributed to this report.