A Youtube video of Marco Rubio filmed by a University of Pennsylvania student has struck at the heart of the GOP presidential race.

Cruz fired his main spokesman, Rick Tyler, on Monday afternoon over a video that falsely showed Rubio dismissing the Bible.

Tyler had apologized late on Sunday for posting "an inaccurate story" involving a video purporting to show Rubio referring to the Bible and saying, "Not many answers in it." Tyler had retweeted a link to the misleading video and posted it on Facebook. Rubio was speaking to a Cruz staffer at the time.

Cruz fired Tyler the next day, saying his campaign did not question the faith of other candidates. "That's why I'm asking for Rick Tyler's resignation," Cruz said.

UPenn's student newspaper, the Daily Pennsylvanian, sent students to cover the Republican primary in South Carolina. They posted a copy of the video shot by a student with quotes from Rubio that Rubio denied making.

Now the Daily Pennsylvanian has stripped the subtitles attributing those comments to Rubio about the Bible and posted an editor's note to their piece — indicating that a Cruz staffer may have allowed a misunderstanding of the video to occur.

"Though our original transcription reflects what we originally heard, after reviewing the audio, we feel it is too unclear to say for sure," the DP wrote. "We showed the staffer in the video this footage on Sunday morning, and he did not correct our transcript. We have reached out to him for comment."

The first-term senators from Texas and Florida are locked in a battle to become their party's alternative to political outsider Trump in Nevada's caucus on Tuesday, the last Republican presidential contest before the busy voting month of March.

Tyler's dismissal came amid intense criticism of the Cruz campaign as dishonest from both Rubio and Trump.

Rubio spokesman Alex Conant called Cruz a "candidate willing to do or say anything to get elected" and urged him to apologize.

"There is a culture in the Cruz campaign, from top to bottom, that no lie is too big and no trick too dirty," he said.

Trump seized the opportunity to pile on Cruz, whom he has repeatedly characterized as a liar.

"Wow, Ted Cruz falsely suggested Marco Rubio mocked the Bible and was just forced to fire his Communications Director. More dirty tricks!" the billionaire businessman from New York said on Twitter.

"Ted Cruz has now apologized to Marco Rubio and Ben Carson for fraud and dirty tricks. No wonder he has lost Evangelical support!," continued Trump, who has derided Cruz for failing to live up to expectations he would get solid support from evangelical Christians in South Carolina.

Trump was the big winner in that state on Saturday, finishing ahead of Rubio by 10 percentage points.

Watch the video of Rubio's comments below to decide for yourself.

Additional reporting by Sam Newhouse