Donald Trump has all but clinched the Republican US presidential nomination with a resounding victory in Indiana that knocked rival Ted Cruz out of the race and cleared his path to a likely November showdown with Democratic front-runner Hillary Clinton.
Billionaire businessman and reality TV star Mr Trump still needs about 200 delegates to formally secure the nomination, but Mr Cruz's decision to end his campaign removed his last major obstacle.
"Ted Cruz - I don't know if he likes me or he doesn't like me - but he is one hell of a competitor," Mr Trump said of his last fierce competitor whom he had dubbed "lyin' Ted".
Mr Trump, in a victory speech that was much lower-key than usual, promised victory in November's general election, vowing anew to put "America first".
Meanwhile Vermont senator Bernie Sanders scored a victory over Mrs Clinton in Indiana, but the outcome will not slow the former US secretary of state's march to the Democratic nomination.
Heading into Tuesday's voting, Mrs Clinton had 92% of the delegates she needed.
Mrs Clinton and Mr Trump now plunge into a six-month battle for the presidency, with the future of America's immigration laws, health care system and military posture around the world at stake.
Mr Sanders said he had won a "great upset victory" in Indiana and expected "more victories in the weeks to come".
"The Clinton campaign thinks this campaign is over. They're wrong," he said.
Mr Sanders said he had an "uphill climb" to the nomination but was "in this campaign to win and we are going to fight until the last vote is cast".
While Mrs Clinton heads into the general election with significant advantages with minority voters and women, Democrats have vowed to not underestimate Mr Trump - as his Republican rivals did for too long.
For months, Republican leaders considered him a fringe candidate and banked on voters shifting toward more traditional contenders once the primary contests began. But Mr Trump proved to be surprisingly durable, tapping into Republicans' deep anger with party leaders and outlasting more than a dozen experienced political rivals.
Republican National Committee chairman Reince Priebus declared the race over, saying on Twitter that Mr Trump would be the party's presumptive nominee.
"We all need to unite and focus on defeating HillaryClinton," he wrote.
Indeed, Mr Trump's first challenge will be uniting a Republican Party that has been rocked by his candidacy. While some party leaders have warmed to the property mogul, others have promised to never vote for him and see him as a threat to Republican existence.
Even before the Indiana results were finalised, some conservative leaders were planning a Wednesday meeting to assess the viability of launching a third party candidacy to compete with him in the autumn.
One outside group trying to stop him suggested it would shift its attention to helping Republicans in other races. Rory Cooper, a senior adviser to the Never Trump super PAC, said the group will help protect "Republican incumbents and down-ballot candidates, by distinguishing their values and principles from that of Trump, and protecting them from a wave election".
Indiana was viewed as the last gasp for fiery Texas senator Mr Cruz. The conservative campaigned aggressively in the state, securing the support of Indiana's governor and announcing businesswoman Carly Fiorina as his running mate, but lost momentum in the closing days.
He had clung to the hope that he could keep Mr Trump from reaching the 1,237 delegates needed for the nomination and push the race to a rare contested convention.
"I've said I would continue on as long as there was a viable path to victory; tonight I'm sorry to say it appears that path has been foreclosed," Mr Cruz told sombre supporters in Indianapolis.
Ohio governor John Kasich is now the only other Republican left in the race, but he has won just one primary - his home state - and trails Mr Trump by nearly 900 delegates.
Mr Kasich pledged to stay in the race, with his campaign manager saying he would continue to "offer the voters a clear choice for our country".
Only about half of Indiana's Republican primary voters said they were excited or optimistic about any of their remaining candidates becoming president, according to exit polls. Still, most said they probably would support whoever won for the party.
Mrs Clinton, too, needs to win over Mr Sanders' enthusiastic supporters. Mr Sanders has cultivated a deeply loyal following, in particular among young people, a group Democrats count on in the general election.
Mr Sanders has conceded his strategy hinges on persuading superdelegates to back him over the former US secretary of state. Superdelegates are Democratic Party insiders who can support the candidate of their choice, regardless of how their states vote. And they favour Mrs Clinton by a nearly 18-1 margin.
Exit polls showed about seven in 10 Indiana Democrats said they would be excited or at least optimistic about either a Clinton or Sanders presidency. Most said they would support either in November.
The exit polls were conducted by Edison Research for The Associated Press and television networks.
With his narrow Indiana victory, Mr Sanders picked up at least 43 of the state's 83 delegates. Mrs Clinton now has 2,202 delegates to his 1,400. That includes pledged delegates from primaries and caucuses, as well as superdelegates.
Mr Trump now has at least 1,047 delegates, Mr Cruz exits the race with 565, while Mr Kasich has 152.