Santorum has defended his votes for such projects, saying the money added up to a fraction of federal spending.
"We are focused on a little bit and we're ignoring the elephant in the room," he said Thursday in Hilton Head. He argued for nominating a candidate who can draw a clear contrast with President Barack Obama.
Romney isn't the one, Santorum said.
"We need contrasts, not just a paler shade of what we have," Santorum said
The former senator's vote against a bill to ban compulsory union membership nationally may also cause him trouble as the issue is particularly touchy in South Carolina.
State unemployment has dropped to just below 10 percent due to manufacturers such as BMW, Fuji and Michelin expanding in the state because the law blocks mandatory union membership. The law is at the heart of the National Labor Relations Board's challenge to Boeing's decision to build a new airplane plant in South Carolina.
"Standing on the opposite side of right-to-work is a costly proposition in this state," said Adam Temple, a Republican operative who worked on 2008 presidential candidate John McCain's South Carolina campaign.
Santorum signed a pledge to support national right-to-work legislation as president. He also has defended his vote by arguing in part that unions, powerful in his home state of Pennsylvania, also are forces of good in the community.
Santorum's backers hope that if he takes a hit with fiscal conservatives he'll make up for it with big support among social conservatives, given his rock-solid opposition to abortion and gay rights.
That's what attracted Violet Stephens to Santorum.
"He has the message that relates to the issues I feel strongly about," said the retired preschool teacher from Greenville. "He's a good Christian man."
Joe Mack, a Santorum supporter and former public policy director for the state's Southern Baptist Conference, predicted that attacks on Santorum's votes in Congress likely won't work in South Carolina, especially among voters who put cultural issues first. Mack said momentum for Santorum will build if he can get his message across to evangelicals.
"The next several days will be critical for him," Mack said.
Associated Press writers Brian Bakst and Philip Elliott contributed to this report.
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