The Republican candidates running for US president have attacked frontrunner Donald Trump in their first debate.
The tycoon, who has upended the race with controversial comments about war heroes and Mexicans, was centre stage.
He was immediately criticised by Rand Paul for being the only candidate who refused to rule out a third-party run against any eventual Republican winner.
The 10 candidates on stage in Cleveland were selected by Fox News on the basis of recent national polls.
The 90-minute forum, which began at 9pm local time (01:00 GMT), featured some frank exchanges as candidates vied to stand out in such a crowded Republican field.
Earlier, Carly Fiorina mocked Mr Trump’s links to the Clintons in a separate Republican debate for the seven candidates that failed to make the main event.
In both debates, immigration reform, abortion and foreign policy were among the issues that candidates were questioned on.
On Thursday, the Democratic Party announced they will hold their first debate in Nevada in October, hosted by CNN.
The Republican top 10
- businessman Donald Trump
- former Florida Governor Jeb Bush
- Wisconsin Governor Scott Walker
- former Arkansas Governor Mike Huckabee
- surgeon Ben Carson
- Texas Senator Ted Cruz
- Florida Senator Marco Rubio
- Kentucky Senator Rand Paul
- Ohio Governor John Kasich
- New Jersey Governor Chris Christie
A fun guide to the 10 Republican debaters
Meet all the 2016 hopefuls
The format, which narrowed the field of 17 contenders to 10, has been criticised by some as unfair.
Former Pennsylvania Senator Rick Santorum reacted angrily to his omission.
He and the six other remaining candidates took part in an earlier debate that featured several attacks on Mr Trump.
Former Texas Governor Rick Perry said he was running a campaign based on celebrity, while former Hewlett-Packard CEO Carly Fiorina mocked him over his Clinton ties.
Influential figures at Fox News, including presenters Chris Wallace and Bill O’Reilly, declared Ms Fiorina the winner.
Former senator Rick Santorum called the Supreme Court’s decision on same-sex marriage a “rogue” decision, comparing it to another ruling, Dred Scott, which said African Americans were not citizens, and was later overturned.
Ms Fiorina, the only female in the race, also slammed Democratic candidate Hillary Clinton.
“She lies about Benghazi, she lies about emails and she supports funding Planned Parenthood,” she said.