Donald Trump's Republican rivals tried to present themselves Wednesday night as the ideal candidates to block the real estate billionaire's path to the GOP nomination and then beat Democratic frontrunner Hillary Clinton in the general election. 

Speaking at a special forum in Houston hosted by Fox News' Megyn Kelly, Texas Sen. Ted Cruz called on Republican voters Wednesday to unite around his campaign, saying that his was "the only campaign that can beat Donald [and] has beat Donald," a reference to his win in last month's Iowa caucuses.

Ohio Gov. John Kasich and retired neurosurgeon Dr. Ben Carson shrugged off calls for them to quit the race, with Kasich saying he would beat Trump in a head-to-head contest.

At one point, Kasich sparred with Kelly, who said Republicans "see you, even though they like you, struggling to get above bottom rung [and] question whether you're stealing votes from candidates who could actually win."


"I'm husbanding my resources," Kasich responded. "The people calling for me to get out are the people who are inside the Beltway ... I'm certainly not listening to a bunch of lobbyist insiders."

However, Kasich said that Trump would likely keep his run of victories going over the next couple of weeks, but claimed that the Republican Party's proportional system of delegate allocation would keep his campaign viable.

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Carson noted that only a small fraction of the current delegates had been awarded through the first four contests, saying "We have a long way to go." Carson later encouraged an audience questioner to "stop listening to the pundits and listen for yourself. Look at the candidates running ... and you can see how consistent they are."

Florida Sen. Marco Rubio, who has finished second in each of the last two nominating contests, acknowledged that Trump was "the frontrunner and I'm the underdog, but I've been an underdog my entire life." Rubio added that his campaign "would not allow the conservative movement to be defined by a nominee who isn't a conservative."

Rubio also took a shot at Trump, though he did not mention that candidate's name, for his remarks on Muslims.


"When you're president, you have an enormous megaphone," Rubio said, "You get to set the tone and agenda for the entire country. We already have a president that's incredibly divisive. We should not be pitting and dividing Americans against each other."

The forum was held six days before a dozen states hold primaries and caucuses as part of Super Tuesday, during which 595 delegates will be awarded. 

"I think he's got a fairly low ceiling," Cruz said of Trump, who won Tuesday's Nevada Republican caucuses for this third straight convincing victory. "In the head-to-head polls, Donald consistently loses to [Democratic frontrunner] Hillary [Clinton]. I consistently beat Hillary."

"And if Donald does win the general election, who knows what the heck he'll do as president?" Cruz asked.

Cruz reserved his strongest language for Planned Parenthood, which he referred to as a "criminal enterprise" and the reason "millions of young boys and girls have never breathed a breath of fresh air."

He repeated his vow to order a Justice Department investigation of the healthcare provider "on day one" of his presidency and took another shot at Trump for saying that Planned Parenthood "does do wonderful things" during a debate in South Carolina earlier this month.

"There are a lot of things Donald has said that I disagree with," Cruz said, "and that is very near the top."

Carson got one of the biggest reactions of the evening when he explained his comment earlier this week that President Barack Obama was "raised white."


"He was raised by his white grandma in Hawaii in a very affluent area [with] a private school [education] and spent his formative years in Indonesia with his white mother," Carson said. "Now, if that's a typical black experience ..." as the audience broke out laughing. 

Carson went on to call the media firestorm over his remarks "ridiculous analysis" designed "to ridicule me and divide wedges."