Sen. Ted Cruz (R-Tex.) is leaving nothing to chance as he tries to take down GOP presidential rival Donald Trump.

On Sunday, in an interview with ABC's George Stephanopoulos on "This Week," he suggested that Trump's unreleased tax returns could show "business dealings with the mafia."

"There have been multiple media reports about Donald's business dealings with the mob, with the mafia," Cruz said. "Maybe his tax returns show those business dealings are a lot more extensive than had been reported.… We don't know."

The Republican primary veered into tax returns this week when Cruz and Sen. Marco Rubio (R-Fla.) released the past five years of returns in an effort to put pressure on Trump to release his. The billionaire has delayed releasing his, citing an IRS audit. Mitt Romney, the 2012 Republican nominee, predicted that there would be a "bombshell" in Trump's tax returns.

In an interview with Chris Wallace on "Fox News Sunday," Trump repeated that he would not release his tax returns right now.

Cruz's mafia comment comes just days before a potential make-or-break election for his campaign. Many political observers think he has to win his home state of Texas in the 11-state Super Tuesday contest to stay viable in the race. But with Trump's continued dominance in the race, not even that is a given.

On Sunday, Cruz appeared on all the major five news shows — what's known as a "Full Ginsburg." In an interview with CNN's Jake Tapper on "State of the Union," Cruz asked Republican primary voters on Tuesday to vote for him — "even if you like another candidate."

"If you want to stop the Trump train," he said, "the only way to do this is to beat him."