Republican presidential candidate Ted Cruz (R-Tex.) said he asked campaign spokesman Rick Tyler to resign after he posted a tweet about rival Marco Rubio (R-Fla.) (Reuters)

LAS VEGAS -- Sen. Ted Cruz (R-Tex.) has parted ways with Rick Tyler, his longtime campaign spokesman, attempting to put an end to Florida Sen. Marco Rubio's accusation that the Texan is trying to win the Republican presidential nomination with dirty tricks.

"Yesterday, a staffer from our campaign sent out a tweet that tweeted a news story that purported to indicate Marco saying something negative about the Bible," Cruz said. "The news story was false. That staffer deleted the tweet, apologized, and pulled it down, although I've spent this morning investigating what happened. And this morning, I asked for Rick Tyler's resignation."

Cruz made the remarks before a campaign rally of around 800 potential voters in the western suburbs of Las Vegas. An 11:30 a.m. news conference was pushed back 40 minutes, as Cruz huddled with aides in the parking lot of a YMCA. Tyler did not respond to a question from The Washington Post, but NBC reporter Katy Tur tweeted that he walked off the set before an interview, scheduled right when Cruz was talking to reporters.

Tyler's offense had not, initially, looked like the sort of mistake that could cost someone his job. The Daily Pennsylvanian, the student newspaper at the University of Pennsylvania, had published a 21-second video of Rubio walking past a Cruz staffer and Cruz's father, Rafael. According to the paper, the muffled audio found Rubio joking that there were "not many answers" in the book the staffer was reading -- the Bible.

The video went viral. Tyler posted it on Facebook. (Cruz mistakenly said he had done so on Twitter.) Then, upon learning that the transcript was exactly wrong -- that Rubio had said "all the answers" were in the Bible -- Tyler wrote a late-night Facebook post apologizing to Rubio.

The senator did not quite accept the apology. At a morning gaggle with reporters in north Las Vegas, near where he spent parts of his childhood, Rubio called the errant post “part of a pattern” of dishonest tactics by the Cruz campaign.

“Perhaps that was the most offensive one because they basically made it up," Rubio said. "People in a lobby taking a video on their phone. I know exactly what I said to that young man. I said the answer to every question you’ll ever have is in that book. And then I pointed to the Book of Proverbs, which he was reading; I said particularly that one, which is a book of wisdom.”

Rubio said he accepted Tyler’s apology, but added that “at some point there was to be some level of accountability.”

But the firing of Tyler came as a surprise. As recently as last night, the Cruz campaign considered the Rubio campaign's outrage over the tweet to be just the latest example of a candidate with friendly media coverage using it to accuse Cruz of negative campaigning. In the final days of the South Carolina primary, the Cruz campaign found itself responding to sketchy accusations of robocalls or online chatter spreading rumors that Rubio would quit the race.

Those attacks looked to be sticking, thanks to a pincer attack from Rubio and Donald Trump. Both have accused Cruz of spreading the rumor that Ben Carson was quitting the race on the night of the Iowa caucuses -- something that a few overzealous Cruz precinct captains actually did, after a CNN story about Carson taking some downtime was misinterpreted.

Earlier in the news conference, Cruz appeared to be digging in, saying that both Rubio and Trump were getting away with "fabrications" about his record. Before taking a question about Tyler, Cruz fielded two about whether Donald Trump was, respectively, "unstoppable" or "unbeatable." And on the way out of the news conference, Cruz denied reports that he had met or talked to Rubio since the incident.

"None of you have heard me throw the kind of insults at Marco Rubio that he throws at me every single day," said Cruz. "When other candidates choose to go into the gutter, we will not do the same. Rick Tyler is a good man. This was a grave error of judgment. It turned out the news story he sent out was false, but I'll tell you, even if it was true, we are not a campaign that is going to question the faith of another candidate."

The Rubio campaign, once again, took the apology as a chance to ask for more.

"Rick is a really good spokesman who had the unenviable task of working for a candidate willing to do or say anything to get elected," said Rubio spokesman Alex Conant in a statement. "There is a culture in the Cruz campaign, from top to bottom, that no lie is too big and no trick too dirty. Rick did the right thing by apologizing to Marco. It's high time for Ted Cruz to do the right thing and stop the lies."