Ted Cruz has announced he is ending his campaign for the US Republican presidential nomination, after losing heavily to Donald Trump in the Indiana primary.
Mr Trump, a New York businessman who is unpopular with many in his own party, is almost certain to be the nominee.
Earlier, Mr Cruz called Mr Trump a “liar” who was unfit to be president. In the Democratic battle, Bernie Sanders is projected to beat Hillary Clinton in Indiana.
He trails Mrs Clinton in the all-important delegate count but after this victory he said the contest was still alive.
“Clinton campaign thinks this campaign is over. They’re wrong,” he said.
Mr Cruz’s advisers had targeted Indiana as the Texas senator’s best hope of halting Mr Trump’s march to the nomination.
“We gave it everything we’ve got, but the voters chose another path,” he told supporters in Indiana.
His departure means Mr Trump is the presumptive Republican nominee, sure to reach the 1,237 delegates required to win.
The New York businessman is the first nominee since Dwight Eisenhower in 1952 to lack any previous experience of elected office.
The Cruz party is over – Anthony Zurcher, BBC News, Indianapolis Turn out the lights, the party’s over. Ted Cruz and the #NeverTrump movement threw everything they had at Donald Trump in Indiana, and it wasn’t enough.
It wasn’t even close to enough.
They outspent him by more than a million dollars. Mr Cruz practically took up residence in the state for the past two weeks. He named Carly Fiorina as his running mate. Nothing worked.
If there was a defining moment of the Indiana campaign, it was Mr Cruz’s fruitless attempt to reason with a group of pro-Trump supporters on Sunday. Every argument he advanced was rebuffed. Every bit of evidence of Trump malfeasance was denied. Mr Cruz was shouting in the wind.
In the coming days, there will be a great reckoning as the party comes to terms with the prospect of Mr Trump as their standard bearer in the autumn.
Some will make peace. Some will despair. Others will say “I’m with her” and reluctantly move to Hillary Clinton’s side.
It will be an unprecedented spectacle in modern US political history.
The verbal attacks between him and Mr Trump had reached a new level of intensity on Tuesday.
Mr Cruz attacked the billionaire businessman as “totally amoral”, “a pathological liar” and “a serial philanderer”.
Mr Trump responded by calling Ted Cruz a “desperate candidate trying to save his failing campaign”.
But hours later, after Mr Cruz announced he was quitting the race, Mr Trump praised him as a “tough, smart competitor”.
It is looking increasingly likely that Mr Trump will face Mrs Clinton in the autumn in the battle to succeed President Barack Obama, who will be leaving the White House after two terms.
But Republicans have expressed reservations about Mr Trump’s outspoken remarks, which have offended women and Hispanics.
There are also concerns about some of his policies on immigration and national security, like building a wall on the southern US border paid for by Mexico, a ban on Muslims coming to the US and the killing of the families of terrorists.