Republicans Get Dirty at Insult-ridden Presidential DebateDismissing his rivals as "lying Ted" and "little Marco," Donald Trump fended off intense attacks from his fellow presidential hopefuls at a debate Thursday that comes amid deeps signs of divisions within the Republican Party. During the debate, Florida Senator Marco Rubio, Texas Senator Ted Cruz and Ohio Governor John Kasich took turns taking swipes at the New York businessman, who appears to be marching toward the party's nomination. The debate, being held in the northern city of Detroit, was filled with the same yelling, personal insults and off-color remarks that have featured prominently in the 2016 Republican race for president. Within five minutes of the debate's opening, Trump had seemingly bragged about the size of his genitals. "[Rubio] said if my hands were small, then something else is small," Trump said, holding up his hands. "I guarantee there's no problem. I guarantee you." Trump was referencing a comment made by Rubio last week that was widely seen as a reference to the businessman's sexual prowess.  Rubio: Donald 'deserves' attacks Rubio defended his attacks, saying it was Trump who started the insults. "For the last year, Donald Trump has basically mocked everybody with personal attacks," Rubio said. "If there's anyone who's ever deserved to be attacked that way, it's Donald Trump." The bitter Trump-Rubio rivalry continued Thursday, with the ex-reality television star referring to the Florida senator as a "little guy [who] has lied so much about my record." Rubio fired back: "You ask him a question about the economy and the first thing he does is go into the 'little guy' thing," Rubio said. Cruz, who had a stronger than expected performance during this week's crucial Super Tuesday nominating contests, also slammed Trump's vitriolic style. "I think that the American people understand that yelling and cursing at people doesn't make you a tough guy," he said. "Nominating Donald would be a disaster," Cruz said. The low-polling Kasich stayed out of the political dog fight. "I have never tried to go and get into these kinds of scrums that we are seeing here." Kasich said. "People say, wherever I go: 'You seem to be the adult on stage.'" Trump: Romney a 'failed candidate' The debate began with a question about someone not on stage: Mitt Romney. The party's most recent nominee strongly criticized Trump in a speech Thursday, calling him a "con man" and a "phony" who is "playing the members of the American public for suckers." Asked to respond to the criticism, Trump dismissed Romney as a "failed candidate" who was "an embarrassment to everybody" when he lost to President Obama in 2012. "Obviously he wants to be relevant; he wants to be back in the game," Trump said. At an earlier news conference, Trump used even more direct language, saying Romney once "begged" for his endorsement during his 2012 presidential run. "I could have said, 'Mitt, drop to your knees.' He would have dropped to his knees,'" Trump said, in what was widely interpreted as a thinly veiled sexual joke.  Republican split Trump's bombastic style and often extreme positions have alienated many within the Republican Party. Many Republican lawmakers and leading party figures have said they will never support Trump, even if he is the nominee, while others have begun to coalesce behind him. Asked whether they would support the eventual Republican nominee, Cruz, Kasich and Rubio all said they would, even while insisting they had not given up the fight against Trump. It is increasingly unclear what party leaders can do to stop Trump, who has a commanding lead both in national polls and in the count of delegates needed to win the nomination. Heading into Thursday's debate, Trump is the only Republican candidate on track to win the necessary 1,237 delegates, according to the well-respected Cook Political Report.