Newt Gingrich, the Republican White House hopeful, is leading in at least four opinion polls, hours before the presidential primary in the southern US state of South Carolina.

Public Policy Polling said that 35 per cent of registered Republicans in South Carolina supported Gingrich, a former congressman and House of Representatives speaker, over the previous front-runner, Mitt Romney, who received 29 per cent of the support.

The two candidates are both trailed by the former Pennsylvania senator, Rick Santorum, and the former congressman, Ron Paul.

Al Jazeera's reports from South Carolina.