Donald Trump to GOP establishment: 'Embrace what's happening'.

Republican presidential front-runner Donald Trump opened the CNN debate here Thursday by calling on his party leadership to "accept" what is happening in the 2016 election.

Trump, who is dominating the GOP primary season, said his campaign has spurred unprecedented enthusiasm and turnout.

"The Republican establishment, or whatever you want to call it, should embrace what's happening," Trump said.

A week after the last raucous Republican debate at which Trump boasted about the size of his manhood, Thursday's forum struck softer tones -- at least initially. Personal insults that dominated previous debates were largely absent, replaced instead by a policy-oriented discussion on issues including immigration and Social Security.

"So far, I can't believe how civil it's been up here," Trump quipped.

Trump addressed an issue that has tripped him up in the past: H-1B visas that encourage legal immigration for high-skilled workers.

He called the program "very, very bad for workers," but in the same breath, acknowledged that he uses it in his hiring practices.

"I know the H-1B very well. I use it. I shouldn't be allowed to use it," Trump said, adding that the program should simply not exist.

Trump or Cruz? GOP leaders shake their heads, prepare to choose

Trump and three other White House hopefuls at the debate are heading into a week that could alter the course of the 2016 election. Trump is at his usual spot at center stage. With a sizeable lead in the delegate race, the New York billionaire holds the best chance of clinching the Republican Party's nomination. To his left is Texas Sen. Ted Cruz, who -- bolstered by his recent primary victories -- is urgently pleading with the party to help him defeat Trump.

Marco Rubio and John Kasich may have the most to gain or lose. Both have had a disappointing few months and badly trail in the delegate path. Next Tuesday, each man will face the voters of their respective home states of Florida and Ohio. For both candidates, losing those contests would likely be the death knell for their campaigns.

The outcomes in Florida and Ohio will be critical in shaping the course of the GOP race. A Fox News poll released Wednesday showed Kasich with a narrow lead ahead of Trump in Ohio; in Florida, Trump was well ahead of Rubio.

Ted Cruz's challenge: uniting Republicans against Trump

If this poll bears out and Kasich is able to eke out a win in Ohio, that could suddenly make him the establishment favorite and earn him fresh support from party leaders and donors uncomfortable with the idea of Trump or Cruz becoming the nominee.

If Trump, as he is predicting, wins both Florida and Ohio and picks up the 165 delegates that are at stake in the two winner-take-all states, his candidacy would turn into a runaway train.

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