Donald Trump is now questioning Marco Rubio's eligibility

Republican presidential frontrunner Donald Trump has been threatening to sue opponent Ted Cruz over his eligibility to hold the nation's top office. Now, it seems, Trump has another target: Marco Rubio.

On Saturday, Trump retweeted the following message about Cruz and Rubio:

"@ResisTyr: Mr.Trump...BOTH Cruz AND Rubio are ineligible to be POTUS! It's a SLAM DUNK CASE!! Check it! https://t.co/NjqWP0pP6X"

— Donald J. Trump (@realDonaldTrump) February 20, 2016

ABC's George Stephanopoulos pressed the Rubio point Sunday on This Week. In response, Trump hedged. A lot.

"I honestly have never looked at it. As somebody said, [Rubio's not eligible]. And I retweeted it," Trump said. "I have 14 million people between Twitter and Facebook and Instagram and I retweet things and we start dialogue and it's very interesting."

Rubio was born in Florida to Cuban immigrants.