Former House Speaker Newt Gingrich called the investigation into Russian interference into the election, and if President Trump obstructed that investigation, is a "legalistic nightmare" that's trying to block his agenda.

Gingrich, an outspoken defender of Trump who is promoting a book he's written about the new president, said on ABC on Sunday that questions about whether Deputy Attorney General Rod Rosenstein should follow Attorney General Jeff Sessions' lead and recuse himself from the Russia investigation are just a distraction.

"This whole game of recusal now, this is a nightmare," he said. "I don't think people realize this: You have this legalistic nightmare trying to block the Trump presidency."

Gingrich said there's no evidence Trump colluded with the Kremlin in order to win the 2016 presidential election and called the rumors swirling around the administration unfounded speculation.

He said there's no evidence of a crime committed by Trump and that means there shouldn't be an investigation into the president.

"If you don't have a crime, what is it you're investigating?" he said.

He added, "No one has suggested that Donald Trump had anything to do with collusion with the Russians. There's not a bit of evidence of that."

He called on lawmakers investigating Trump's administration, and the FBI, to show their proof of Trump possibly being involved in any collusion with Russia.

"If you have any evidence that Donald Trump is personally involved, then show it," he said.