Paul Ryan. AP Photo/J. Scott Applewhite

Donald Trump on Monday accused House Speaker Paul Ryan of distancing himself from Trump because he is thinking about his own presidential aspirations for 2020.

Questioning Ryan's motives, Trump implied in an ABC News interview that the speaker did not care whether Trump won the White House: "Well, maybe not," Trump said, "because maybe he wants to run in four years or maybe he doesn't know how to win."

"Maybe he just doesn't know how to win," Trump added. "I mean, who can really know? But I know I'm in his territory and they are all screaming for Trump."

The Republican presidential nominee held a campaign rally in Ryan's home state of Wisconsin on Monday in which the crowd chanted "Paul Ryan sucks" and Trump railed against what he called "corrupt" media and a "rigged" election system — a frequent accusation the Manhattan billionaire has brought up without evidence.

The chairman of the Wisconsin Republican Party, Brad Courtney, later defended Ryan in a statement, saying: "The Republican Party of Wisconsin is incredibly proud and fully supportive of Speaker Paul Ryan and the work he does for the conservative movement here in Wisconsin and across this great nation."

Ryan's fraught relationship with Trump worsened after the release two weeks ago of a 2005 recording that showed Trump bragging about groping women.

After the leak, Ryan disinvited Trump from a Wisconsin campaign event and said he would no longer defend Trump against any further controversies that might emerge before Election Day. He did not, however, rescind his endorsement of Trump.