Donald Trump and fellow GOP presidential candidate Ted Cruz clashed on Thursday in the most personal and sharpest encounters thus far in the ongoing campaign season.

Trump said following the debate that the “bromance” has ended.

The event, which lasted 2 ½ hours was sponsored by the Fox Business Network and was filled with a serious of testy exchanges between each of the seven GOP candidates on state.

Trump and Cruz are in a battle to win the Iowa caucuses, which are just over two weeks away, though nationally the real estate mogul holds a commanding lead.

With pressure increasing for one candidate to emerge as an alternative for the establishment to Cruz and Trump, sparks also flew between Florida Senator Marco Rubio and New Jersey Governor Chris Christie.

The showdown between Trump and Cruz was much anticipated and took a couple of minutes to materialize but it packed a big punch all the same.

Cruz responded forcefully to accusations by Trump that he is not eligible to be the president since he was born outside the U.S., a controversy Trump has just recently embraced.

Cruz said that during September his friend, Mr. Trump and lawyers had looked at that every way possible and there was nothing on the issue. Since September, he added, the Constitution has not changed, but poll numbers have.

While plenty of animosity has existed amongst Trump and the majority of rivals, the businessman and Cruz have largely been friendly for the majority of this campaign season.

However, that changed when the polls began tightening in Iowa ahead of the caucuses on February 1.

Trump hopes to eat into the Texas Senator’s Iowa support and has repeatedly questioned if Cruz, whose mother was a citizen of the U.S., is a natural born citizen.

However, in the attack against Trump Thursday, Cruz noted some of the extreme theories of being able to run for the presidency, of which one is both parents must be born in the U.S. and that would mean Trump would be ineligible as well since his mother was born in Scotland.