Gingrich on the brink, with Romney poised to pull away in Deep South

In one of the closest fought Republican primaries to date, the polls can't split the main candidates

One survey gives Newt Gingrich a one point advantage over Mitt Romney in the Mississippi primary (AP)

Surprise victories tomorrow in one or even both of the Deep South states voting in the Republican nomination marathon could all but sew it up for Mitt Romney and leave his rivals scrambling for relevancy.

Eve-of-voting polls in both Mississippi and Alabama showed surprising strength for the former Governor of Massachusetts, upending assumptions about his lacking support in the South.

An American Research Group survey last night showed him edging out Newt Gingrich 34 per cent to 32 per cent to win Alabama. A Public Policy Polling survey in Mississippi gave Mr Gingrich a mere one point edge over Mr Romney.

Mr Gingrich's southern strategy, based on his two earlier wins in South Carolina and Georgia, will crumble if he fails to score, as will his reasoning for staying in the race. Were he to withdraw, the boost to Rick Santorum would be invaluable. A double-win by Mr Romney could finally derail both Mr Gingrich and Mr Santorum.

So far the South has largely shut out Mr Romney, but today he may benefit from the splitting of the conservative vote between Mr Gingrich and Mr Santorum. Yesterday, Mr Santorum, who is also near the top in polls in both states and who convincingly won caucus voting in Kansas at the weekend, asserted again that Mr Romney would prove unacceptable to the party grassroots.

The muddle at the top of the polls in the two states voting today – Ron Paul, the libertarian, is way down in both – means it will be as tense as any since the long slog began ten weeks ago. "All we know for sure about Tuesday's primaries is that Ron Paul will finish last in them," Dean Debnam, president of Public Policy Polling, commented. "Beyond that it's plausible that any of the candidates could finish between first and third."

Predictions of long-term doom for Mr Romney seem somewhat delusional given his already wide lead in delegates to the national convention. Going into today, Mr Romney has an estimated 454 delegates compared to 217 for Mr Santorum, 107 for Mr Gingrich and a mere 47 for Mr Paul.

"Governor Romney will not make it," Mr Santorum flatly told NBC News. "They are not going to nominate a moderate Massachusetts governor who's been outspending his opponent 10-1 and can't win the election outright. What chance do we have in a general election if he can't, with an overwhelming money advantage, be able to deliver any kind of knockout blow to other candidates?"

A memo attributed to political advisors to Mr Santorum and leaked to the media contained an apparent acknowledgement that catching Mr Romney looks nigh impossible and that dethroning him may have to wait until the party's convention in the summer.

"Mitt Romney must have a majority on the first ballot in order to win the nomination because he will perform worse on subsequent ballots as grassroots conservative delegates decide to back the more conservative candidate," it argued. "Subsequently, Santorum only needs to be relatively close on the initial ballot in order to win on a later ballot as Romney's support erodes."