By Steve Holland
Republican presidential candidates may find themselves in a more subdued debate than usual in Miami, since nothing Donald Trump's rivals have thrown at him has made a major dent in his front-running campaign.
After the histrionics of last week's gathering in Detroit, the four remaining candidates are likely to search for higher ground as they offer closing arguments to Republican voters, particularly those in Florida and Ohio, who vote next Tuesday in nominating contests for the November 8 election.
The burden is particularly heavy on US Senator Marco Rubio of Florida and Ohio Governor John Kasich, who must do well in their home states or face pressure to exit the race.
While Kasich is holding his own against Trump in Ohio opinion polls, Rubio has lagged far behind Trump in Florida.
Trump's victories in Michigan, Mississippi and Hawaii on Tuesday added to his momentum after a week of attacks by mainstream Republicans who are offended by his statements on Muslims, women and illegal immigrants, and alarmed by his threats to international trade deals.
Trump defended his calls for a tougher US stance on free trade on Thursday, saying the United States has been taken advantage of in negotiations with other countries. He also cited currency devaluations as a particular problem.
"I like free trade but you have to be represented by very, very good and smart and cunning people and we are not," Trump said in an interview on CNBC.
"Other countries are and that's why they're all taking advantage."
The tough-talking billionaire businessman told CNN on Wednesday he expected the debate to be a "nicer, softer, lighter debate, I hope".
But he added: "I'll be ready. I'm the only one who can beat Hillary [Clinton]".