CHARLESTON, S.C. - Jeb Bush, John Kasich and Marco Rubio are locked in a high-stakes political chess match in South Carolina in a bid to pull ahead in the Republican primary race - or at least keep their campaigns afloat if they don't.
The manoeuvring comes as some Republican leaders fear Donald Trump or Ted Cruz will begin piling up the delegates needed to secure the nomination before one of the more mainstream candidates can consolidate the support of voters turned off by the brash billionaire and Texas senator, who so-called establishment Republicans believe could jeopardize the party's chances of winning in November's general election.
"We do need to get the field down to Trump, Cruz and somebody," said Henry Barbour, a Republican National Committee heavyweight from Mississippi.

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The Democratic field is already down to two candidates - Hillary Clinton, the former Secretary of State, and Vermont Sen. Bernie Sanders. Clinton is counting on strong support among African-Americans who twice backed her husband, former President Bill Clinton, to act as a firewall against the surprisingly strong insurgent campaign of Sanders.
The only thing that is clear heading into Saturday's pivotal Republican primary in South Carolina appears to be Trump's grip on the lead following his victory in the New Hampshire primary. Cruz, the winner of the Iowa caucuses, is also in the mix for a strong finish.
But the more mainstream lane populated by Bush, Kasich and Rubio is more jumbled. Bush's campaign now sees an opening to capitalize on Rubio's fifth-place finish in New Hampshire, while Kasich's strong second-place showing there has given the Ohio governor reason to keep his campaign going until primaries in friendlier territory in the Midwest. Rubio's team, meanwhile, is quietly confident that South Carolina will prove to be a comeback story for the Florida senator.
Kasich's finish in New Hampshire has scrambled what might have been a do-or-die contest between Bush and Rubio in South Carolina. After initially viewing the first-in-the-South primary as too much of a long-shot for a moderate Midwesterner, Kasich abruptly changed his schedule this week and announced plans to campaign in South Carolina almost every day until Saturday's primary.
"Exceeding expectations is why we're there," Kasich spokesman Chris Schrimpf said.
For Kasich, exceeding expectations would be to finish ahead of Bush, the former Florida governor. Bush has deep family ties to South Carolina - his father and brother each won two Republican primaries here - and a poor showing Saturday could leave him without a compelling rationale to keep his campaign going.
As the third major contest in the primary campaign, South Carolina is accustomed to settling divergent results in Iowa and New Hampshire, with the winner here emerging as the nominee in each presidential cycle from 1980 to 2008. But those typically were two-man contests as the race headed South: Ronald Reagan dispatched George H.W. Bush in 1980, the elder Bush defeated Bob Dole in 1988 and George W. Bush topped John McCain 12 years later.
This time, the gaggle of candidates means there's no clean divide on ideology, personality or anything else.
Even before South Carolina votes, Republican leaders are making the case that candidates who aren't competitive need to swallow their pride and let go of their presidential ambitions.
Katon Dawson, a former South Carolina Republican Party chairman who remains unaligned, put it more bluntly. He said that if a candidate finishes in the single digits Saturday, "you ought to quit."
In the Democratic race, both Clinton and Sanders are making specific appeals to black voters after Sanders won a 22-point victory in last week's New Hampshire' primary, creating a potential opening with black voters for the self-described "democratic socialist."
The Democratic candidates are vying for support in Saturday's Nevada caucuses and then facing off in South Carolina on Feb. 27. Blacks make up more than half of the Democratic primary electorate in South Carolina and several other southern states.
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Associated Press writers Julie Pace and Bill Barrow in South Carolina, and Chad Day and Julie Bykowicz in Washington contributed to this report.