Rick Santorum failed on live television to name one single achievement of Marco Rubio during his five years as Senator in Florida - even though he is endorsing him for president.

The former Pennsylvania Senator dropped out of the presidential race on Wednesday after losing favour in the Iowa caucus and has instead spoken out in favour of his Republican colleague Senator Rubio. But when he was interviewed on MSNBC's “Morning Joe” show, he struggled to say why, as reported by Politico.

Asked for Mr Rubio’s top achievement, Mr Santorum said: “Well, I mean, I would just say that this is a guy who's been able to, number one, win a tough election in Florida and pull people together from a variety of different spots. This is a guy that I think can work together with people. That’s the thing I like about him the most.”

"Morning Joe" host Joe Scarborough pressed again for Mr Rubio’s top achievement during his years as Florida Senator since January 2011.

“If you look at being in the minority in the United States Senate in a year when nothing got — four years where nothing got done, I guess it’s hard to say there are accomplishments,” Mr Santorum said. “I mean, tell me what happened during that four years that was an accomplishment for anybody? It was complete gridlock.”

Mr Scarborough replied that Republicans have been in the majority for two years, not four.

Co-host Mika Brzezinski jumped in: “Jeb Bush ran Florida. Donald Trump built a company. Marco Rubio — finish the sentence.”

Mr Santorum replied it was an achievement to be elected as the speaker of the house in Florida, and blamed President Obama for Republicans “getting nothing done”.

When pressed again, Mr Santorum said there “isn’t a whole lot of accomplishments”.

He also mentioned Mr Rubio’s fight to stop bailing out insurance companies. Mr Rubio took credit for introducing legislation that would prevent taxpayers' money being given to insurance companies as part of Obamacare.

“That’s one thing that I’m familiar with that I just saw recently, but — and again, he was on the campaign trail and accomplished that. The bottom line is there isn’t a whole lot of accomplishments, Joe, and I just don’t think it’s a fair question.”

Speaking to Fox News, Mr Santorum said Mr Rubio had a real sense of the “threat of fundamental Islam” and ISIS and supported the “central role” of family.