Las Vegas (CNN) Donald Trump on Monday night once again ratcheted up his attacks on Sen. Ted Cruz, calling his Republican presidential rival "sick."

He also lashed out at a protester, saying, "I'd like to punch him in the face."

Of Cruz, Trump took aim at the senator's campaign tactics, including the attack ads Cruz and his allies have run against Trump.

"This guy is sick. There's something wrong with this guy," Trump said.

Cruz's campaign has run several ads scrutinizing Trump's record on a variety of issues important to conservatives, including Trump's past support for abortion rights and stricter gun control measures.

The two face off against each other and the rest of the GOP field Tuesday in the Nevada caucuses.

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Cruz campaign: Trump is 'like a frustrated child'

"I missed the part where Donald challenges our facts?" Cruz spokeswoman Catherine Frazier told CNN. "He can't, because our ads are true -- he is not a real conservative. He can't defend his record, so like a frustrated child, he resorts to name calling."

Trump has repeatedly slammed Cruz since the Texas senator surged in the polls ahead of the Iowa caucuses and has since ramped up his attacks on him since Cruz beat Trump in the Iowa contest.

Campaigning in South Carolina last week, Trump also called Cruz "unstable" and "a basket case."

Trump also pointed out Monday that he beat Cruz out for the most support among evangelical voters in the South Carolina primary and said evangelicals voted against Trump because "they don't like liars."

"They're really smart people. They don't want to vote for a liar," Trump said Monday to a crowd of thousands packed into a Las Vegas arena.

Cruz, who has sought to position himself as the one "true conservative" in the race, has ramped up his attacks about Trump, bashing the Republican front-runner for his "New York values" and suggesting Trump is not conservative.

Cruz has criticized Trump over a range of issues, from Trump's support for abortion rights in 1999 to Trump's use of eminent domain laws for personal gain.

Cruz has also suggested that Trump, who has vowed to repeal Obamacare, supports the signature health care law, pointing to Trump's September interview with "60 Minutes" in which Trump said that "everyone's got to be covered" when asked if he supported universal health care.

But Trump has knocked Cruz for more than his attack ads, also pointing to the Cruz campaign's tactics, which included mailers warning voters of a "voter violation" and a Cruz campaign adviser calling grassroots leaders hours before voters headed to the caucuses, claiming that retired neurosurgeon Ben Carson had dropped out of the presidential race. He had not.

Sen. Marco Rubio of Florida, another GOP presidential contender, has also joined Trump in his attacks of Cruz, calling the Texas senator a liar during the last GOP debate.

Trump: 'What the hell is a caucus?'

Trump's Monday rally came on the eve of the Nevada caucuses and Trump spent much of his speech urging his supporters to head to the caucuses to give him what would be his third consecutive victory in the GOP primary.

"They're all saying Trump's gonna win tomorrow. Just assume we're going to tie," Trump told his supporters on Monday night.

And Trump, who has slammed the caucus process since losing to Cruz in Iowa, told his supporters to forget about the slightly more arduous caucus process, which involves voters meeting at a caucus location and hearing pitches for each candidate before casting their vote.

"Forget the word caucus, just go out and vote, OK?" Trump said. "What the hell is a caucus? Nobody even knows what it means."

Trump on protester: 'I'd like to punch him in the face'

Trump also said he wanted to punch a protester "in the face" after a man was escorted out of Trump's rally Monday night.

"I'd like to punch him in the face," Trump said, remarking that a man disrupting his rally was escorted out with a smile on his face. "He's smiling, having a good time."

Trump also claimed the protester was "nasty as hell" and accused the man of trying to punch the security officers forcing him out of the rally, though the man did not appear to be fighting off those officers.

"In the old days," Trump added, protesters would be "carried out on stretchers."

"We're not allowed to push back anymore," Trump said.

While Trump has at times urged his supporters not to hurt protesters, he has also repeatedly suggested that supporters should be handled more roughly.