On Sunday, Rick Tyler, Cruz's communications director, sent social media messages suggesting Rubio had dissed the Bible.

It fed a narrative of the Cruz campaign using nefarious tactics that were undermining his credibility at a critical moment in the GOP presidential race, and the candidate acted swiftly.

"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."

And so a trusted and capable member of Cruz's senior staff is gone for the kind of social media miscue that was once the province of easily jettisoned interns but is now a central and potentially risky responsibility of the top brass in campaigns -- including the candidate himself, in the case of Donald Trump, who has expressed his delight in being able to instantly communicate a pithy message to his 6.3 million Twitter followers.

Trump's politically incorrect tweets only further his reputation for fearless and sometimes baseless bluster.

But Tyler's retweet and posting on Facebook fed a developing meme that the Cruz campaign likes the low road. And it came at an importune time for a campaign trying to regain its mojo after a third-place finish in South Carolina and on the eve of Tuesday's caucuses in Nevada.

"The problem is this mistake fits into a larger narrative of Cruz and dirty tricks," said Paul Begala, a Democratic strategist who helped pilot Bill Clinton's presidential campaigns. "The Carson campaign alleges he misled voters in Iowa about Dr. Carson exiting the race. The Rubio campaign caught Cruz using a doctored photo of Sen. Rubio shaking hands with President (Barack) Obama. Now this."

"Plus, having watched the video, it is not plausible to suggest Sen. Rubio disparaged the Bible," Begala said. "No way someone as slick as Rubio would diss the Bible -- especially not in front of his opponent's preacher/father."

The video captured a chance encounter in the lobby of the Hampton Inn in Columbia, South Carolina, on Saturday morning, election day, in which Rubio happened upon Rafael Cruz reading a Bible with Christian Collins, a young Cruz staffer.

"Got a good book there," Rubio said to Collins.

"Yes, sir," Collins replied.

The audio from then on is not very distinct, but the Daily Pennsylvanian, the student newspaper of the University of Pennsylvania, whose reporters were staying at the same hotel, reported that Rubio then added that the Bible "did not have many answers in it."

Cruz staffers later alerted Tyler that what Rubio actually said was, "All the answers are in there, especially in that one," referring to the book of Proverbs, which is what Collins was reading.

Tyler deleted the posts and apologized, but the damage was done.

Like Begala, Dave Carney, who has served as the top political strategist to Texas Gov. Greg Abbott and former Gov. Rick Perry, said Tyler had to go.

"I have a huge personal bias," Carney said. "Whenever a staff person becomes an issue, they should be fired. It's a distraction. A campaign is bigger than one person or group of people."

"I know Rick," Carney said. "He's a big boy. He's one of the really good guys. He knows how to dish it out, and he can take it."

Carney understands the perils of social media in the heat of a campaign.

"It's a very tense time in a fast-moving, intense environment, you're on Facebook and Twitter all day, and there's an urge to keep the conversation going," he said.

Carney himself is renowned as an edgy tweeter who was called out by Democrats for some of his tweets during the 2014 gubernatorial campaign about Abbott's opponent, Wendy Davis — like the one in which he tweeted "why Wendy Davis is too Stupid to be Governor."

"Sometimes you live on the edge and get away with it, and sometimes you can't," Carney said.

Tyler's retweet was particularly touchy because Cruz is running a campaign aimed especially at evangelical voters that makes much of Cruz's devotion to biblical and constitutional values.

Cruz and his top staffers have prayed together at critical junctures in the campaign, and, in asking for Tyler's resignation, Cruz said he is "a good man" but that, even if the misquote had been correct, "we are not a campaign that is going to question the faith of another candidate for president."

The Rubio campaign responded by praising Tyler's skills but suggesting he "had the unenviable task of working for a candidate willing to do or say anything to get elected."

Meanwhile, Trump, who has accused Cruz of lying while brandishing a Bible, tweeted his own take on Tyler's fate: "Wow, Ted Cruz falsely suggested Marco Rubio mocked the Bible and was just forced to fire his Communications Director. More dirty tricks."