From the article:

The president provided no evidence to back his claim. Current and former intelligence officials from both Republican and Democratic administrations have said that nothing they have seen led them to believe that Ms. Rice’s actions were unusual or unlawful. When Americans are swept up in surveillance of foreign officials by intelligence agencies, their identities are supposed to be obscured, but they can be revealed for national security reasons, and intelligence officials say it is a regular occurrence.

“I think it’s going to be the biggest story,” Mr. Trump said in an interview in the Oval Office. “It’s such an important story for our country and the world. It is one of the big stories of our time.”

He declined to say if he had personally reviewed new intelligence to bolster his claim but pledged to explain himself “at the right time.”

When asked if Ms. Rice, who has denied leaking the names of Trump associates under surveillance by United States intelligence agencies, had committed a crime, the president said, “Do I think? Yes, I think.”