Trump Tweets He Has 'Standing to Sue' Cruz

TAMPA, Florida -- GOP front-runner Donald Trump issued a warning today to rival Sen. Ted Cruz: Keep attacking and a lawsuit is coming.

It all started just after Trump's win earlier this week in New Hampshire, where the Cruz campaign began running multiple ads attacking the billionaire businessman for his support of eminent domain -- that is, the government's power to force the sale of private property for public use.

The Cruz ad features a woman that Trump had a legal dispute with decades ago as he sought to build a parking lot on the property occupied by her home -- in order to expand a casino he once owned in Atlantic City. Trump on the campaign trail has consistently called eminent domain a helpful tool in order to expand both public and private businesses.

The Cruz campaign has now done a large ad buy -- with plans to run a one-minute ad Saturday night during SNL. The news sent Trump into attack mode, digging up an old argument on Cruz's citizenship.

In an interview with the Washington Post in January, Trump was asked if Cruz was eligible to run for the presidency, citing the fact he was born in Canada.

In September, Trump had told ABC News' Jonathan Karl that he felt Cruz was in good standing. But Trump recently said he fears a lawsuit over the fact that Cruz was born in Canada will prevent Cruz from running.

ABC News Chief Anchor George Stephanopoulos told Trump during a recent interview that some legal scholars have suggested Trump himself would have standing to sue Cruz.

"Oh, that's an interesting case. Wow, that sounds like a very good case. I'd do the public a big favor," Trump responded, but would not say whether he'd pull the trigger until issuing this threat today via Twitter: "If @TedCruz doesn't clean up his act, stop cheating, & doing negative ads, I have standing to sue him for not being a natural born citizen."

Trump has also questioned Cruz's "Christian values" with this latest string of attacks from the Texas senator. Trump is scheduled to campaign later today in Tampa, Florida.