Donald Trump takes centre-stage at a debate in Houston as the favourite to win the Republican presidential nomination, with time running out on his remaining rivals to change a race rapidly tilting away from them.
Trump, 69, has won three of the first four contests in the nomination fight for the November 8 election to succeed Democratic President Barack Obama.
After easily defeating his rivals in Nevada on Tuesday, the New York billionaire businessman is in position for more victories on March 1, when a dozen states will vote on “Super Tuesday”.
At a CNN-hosted debate at the University of Houston, Trump’s rivals will have one of their last best chances to try to derail the blunt-spoken political outsider before the Super Tuesday contests.
Whether they can pull it off is an open question.
On stage with Trump will be US Senator Marco Rubio of Florida, US Senator Ted Cruz of Texas, Ohio Governor John Kasich and retired neurosurgeon Ben Carson.
None have been able to slow Trump’s momentum in previous debates.
“Trump is on cruise control,” said Eric Fehrnstrom, a former senior adviser to 2012 Republican nominee Mitt Romney.
He said Trump should ignore his opponents and focus on the key planks in his platform – a border wall to keep out illegal immigrants, a stronger military, defeating Islamic State (IS) and fair trade.
“It’s getting late in the game for everyone else. People who are expecting a sudden shift in the direction of the race are deluding themselves. Trump is Goliath, and we’ve seen enough of the other candidates to know there are no Davids in this field,” Fehrnstrom said.
Rubio, 44, has an added incentive to change the makeup of the race.
He is scrambling to attract the financial donors who supported one-time establishment favourite Jeb Bush, who dropped out of the race after his disappointing finish in South Carolina on Saturday.
Bush, the son and brother of former presidents, held a conference call with his top donors on Wednesday.
A donor on the call said Bush offered effusive thanks for their support but provided no direction on who they should now help.
Cruz, 45, enters the debate under pressure.
He must do well in his home state of Texas on Super Tuesday.
Recently, he has been accused by his rivals of using negative tactics, including one that led to the resignation of his spokesman, Rick Tyler.
Romney, who has yet to endorse a Republican candidate, offered a pathway for attacking Trump, telling Fox News that Trump was bound to have a “bombshell” in his tax records.
“The reason I think there is a bombshell in there is because every time he is asked about his taxes, he dodges and delays and says: ‘Well we’re working on it,’” Romney said.
He added that all the candidates should release their tax records.
“Frankly the voters have a right to see those tax returns before they decide who our nominee ought to be.”
Romney, a businessman and former Massachusetts governor who himself faced relentless questioning about his financial dealings and taxes during the 2012 campaign, said he believed Trump simply might not be as wealthy as he has claimed.
“We could find (that) he doesn’t have anywhere near as much income as we might think he would have with a $10bn net worth, or he doesn’t pay any taxes or he pays very, very low taxes,” Romney said.
The insinuation is reminiscent of a 2012 attack on Romney, when top Senate Democrat Harry Reid repeatedly said an unnamed investor in Romney’s company, Bain Capital, told him Romney “didn’t pay taxes for 10 years”.
Reid’s comments set off a firestorm at the time.
Trump tweeted in response: “Mitt Romney, who totally blew an election that should have been won and whose tax returns made him look like a fool, is now playing tough guy.”
In January 2012 after the start of the primary race, Romney released his tax returns for 2010 and 2011, which showed he earned about $21mn for each of those years.
They also showed that in 2010 he paid a 13.9% tax rate, while those in the top 1%, which clearly includes Romney, paid an average of 23.4%.
Despite his concerns about Trump’s taxes, Romney acknowledged that Trump, who has now won three straight state-wide nomination contests, was the clear frontrunner.
“I think for the other people still in the race their path is becoming a slimmer and slimmer opening,” he said.