The ten Republican presidential candidateswho received the highest levels of supportin public opinion surveysdebated Thursday night in Cleveland, Ohio.The event marked the launch of the 2016 presidential campaign.Billionaire businessman Donald Trumpreceived a lot of attention during the debate,which was shown on the FOX News Channel.He was the only candidatewho would not promise to support whoever winsthe Republican party's presidential nomination.He also refused to sayhe would not campaign for the presidencyas an independent if he did not win the party's nomination.Mr. Trump was asked about controversial statements he has made in the past.He refused to apologizewhen he was questioned about his past insults of women.He also did not apologizefor his statements about illegal immigrants from Mexico.He has said some of them are "criminals" and "rapists."Senators Marco Rubio of Florida and Ted Cruz of Texaswere among candidates who said they support better control of the border with Mexico.Former Florida Governor Jeb Bushcriticized the way Mr. Trump talks about the issue.Several of the candidates strongly criticized the agreement reachedbetween Western powers and Iranto limit that country's nuclear activities.They also criticized the Obama administration's effortsto stop the Islamic State group.Senator Rand Paul and New Jersey Governor Chris Christie argued during the debateabout how to protect Americans while respecting their rights.At one point, Governor Christie called Senator Paul's ideas about security policy "completely ridiculous."The argument between the two menshowed the tension within the Republican Party.One side wants stronger national security policieswhile the other is concerned about the federal government's power.Mr. Bush is considered the choice of many Republicans.He said he knows he must work to be seen asdifferent from his brother and father,both of whom are former presidents.He said the invasion of Iraq by American forces,which was ordered by President George W. Bush, was a mistake.But he blamed President Obama for leaving Iraq too early.He says this led to the creation of the Islamic State, or ISIS.Before the debate on Thursday night,seven Republican presidential candidateswho have lower support in public opinion surveys gathered.Many of them strongly criticized Hillary Clinton.Many experts believe Ms. Clintonwill be the Democratic party's nominee for president.At least eight more Republican debates are planned.The Democratic party plans six debates,beginning in October. I'm Christopher Jones-Cruise.