Ted Cruz has seized upon his victories on "Super Saturday" to claim he is the only man able to stop Donald Trump, as the Republican party scrabbles to throw a spoke in the wheel of the New Yorker's political juggernaut.
Cruz dealt his opponent a bloody nose on Sunday (NZT) when he snatched victory in Kansas, a state Trump was expecting to win.
The pair won two states each, with Trump taking Kentucky and Louisiana and Cruz adding Maine to Kansas to take more delegates overall than the frontrunner.
Cruz was capitalising on his surge in momentum, urging his remaining rivals yesterday to drop out and rally behind his fightback.
"I think we will have a manifest uprising," he said on a political chat show. "If you want to beat Donald Trump you've got to beat him at the ballot box, and our campaign is the only campaign that has demonstrated it can do that."
The other two Republicans in the race, Marco Rubio and John Kasich, had poor performances, with Rubio's hopes of being the establishment alternative to Trump now lying in tatters.
A loss in Florida, his home state, which votes next week, will effectively end his campaign, although a win in Puerto Rico had him talking up his chances yesterday.
Cruz, a senator from Texas, heaped pressure on Kasich and Rubio to abandon the race. "I'm having conversations from all sorts of people and we're seeing supporters of other candidates come joining us," he said.
"They're recognising that their candidates were not in a position to beat Donald."
Cruz added 64 delegates to his tally on Sunday, while Trump gained 49. Trump now has 378 delegates to Cruz's 295 as he tries to reach the winning 1237 tally that would remove the establishment's chance of taking the race to a contested convention and nominating an alternative candidate.
Trump, in his victory speech in Florida on Sunday, declared himself primed for a head-on contest with Cruz.
"I would like to take on Ted one-on-one," Trump said, ticking off a list of big states where he believed Cruz had no chance.
But Cruz, spearheading the Stop Trump campaign, said it was essential for the very soul of America that the billionaire businessman was defeated.
"Think about what presidents have meant in history," he said. "Think of Lincoln's Gettysburg Address. Think of FDR saying, 'The only thing we have to fear is fear itself'.
"I think people are asking themselves, 'How would we feel if our children came in repeating the words of the president of the United States if that president was Donald Trump'."
Thevoting continues for the Republicans today in Mississippi, Idaho and Hawaii, and in Michigan for the Democrats.