I'll fight on, vows Gingrich after cutting campaign staff by a third

He is not dropping out, because that is not his style, but Newt Gingrich – the self-possessed former speaker of the House of Representatives – is curtailing his effort to win the remaining primary elections in the Republican nomination race to focus on a possible floor fight at the party convention in August.

The announcement from Camp Gingrich that it is cancelling campaign appearances and laying off about a third of its staff amounts to an admission, after winning only two states so far, that it no longer has any way to amass the delegates needed for Mr Gingrich to be crowned at the Tampa convention.

While Mr Gingrich will now largely abandon the state-by-state grind of primaries and caucuses, he will direct his energies towards preventing Mitt Romney, the clear front-runner, from reaching the 1,144-delegate threshold that would entitle him to claim the nomination in Tampa without debate.

So long as the former Massachusetts Governor is still short of that number, Mr Gingrich said yesterday, "I owe it to the people that helped me for the last year to represent their views and their values." He added: "Romney has to earn this. It's not going to be given to him."

The strategy seems far-fetched. For one, the chances of Mr Romney not attaining the magic number of delegates are looking ever more unlikely. Even if the convention were to begin with no resolution to the race, it seems hardly credible that Mr Gingrich would emerge as the consensus nominee. Mr Romney was last night on his way to Texas to bask today in the expected endorsement of George H W Bush, the former President, which will be seen as further evidence that the party establishment is at last showing willingness to rally behind him.

Mr Romney is narrowly favoured by opinion polls to beat Rick Santorum, his last serious rival, in a key primary in Wisconsin on Tuesday. Polls also show a lead held by Mr Santorum in his native Pennsylvania, which votes next month, vaporising fast. But, in fresh evidence that the primary process is hurting Mr Romney, an ABC-Washington Post poll showed that the number of Americans who view him negatively has reached a new high, 50 per cent. Just as ominously, only 34 per cent viewed him favourably, compared with 53 per cent for President Barack Obama.

Money was surely a big factor behind Mr Gingrich's partial retreat. Data submitted to the Federal Elections Commission showed he had $1.5m cash in hand by the end of February, but faced paying $1.5m in debts.

"One of the things I was told very early on in presidential politics is that you run for president as long as the money hangs on," Mr Santorum said of Mr Gingrich's decisions. He was swift to add: "I think it is time for all the Republican candidates to coalesce behind me. You know, let's just have a conservative nominee to take on Barack Obama. Until that time happens, I'm not going to call on anyone to get out."

If, by the final primary in Utah at the end of June, Mr Romney is still shy of 1,144 delegates, Mr Gingrich would fire up his campaign. "We're going to make sure Newt is ready to win that 60-day period," Joe DeSantis, his communications manager, said. "What we're going to be doing is focus on a campaign strategy that takes it to Obama."

State of play: How the Republican rivals compare

Newt Gingrich

Number of delegates for Republican convention: 135

He is: the former Speaker in the House of Representatives

Known for: leading Republican takeover of Congress in 1994, half-way through Bill Clinton's first term as President

Mitt Romney

Number of delegates for Republican convention: 568

He is: the former Governor of Massachusetts

Known for: signing "Obamacare"-style health reforms into state law when he was governor

Rick Santorum

Number of delegates for Republican convention: 273

He is: the former US Senator for Pennsylvania

Known for: was a rising star in the Senate but lost a third term re-election battle to a Democrat in 2006.