But the House speaker has not pulled his endorsement of Trump, a Ryan spokeswoman told NBC News.
"The speaker is going to spend the next month focused entirely on protecting our congressional majorities," she said.
Ryan hinted that he may think the presidential race is out of reach for Trump, telling lawmakers on a call that he wants to ensure Democrat Hillary Clinton does not get a blank check with Congress, according to NBC News. He said representatives need to do what is best in their districts.
His decision follows outrage over a leaked 2005 video that shows the GOP presidential nominee crudely joking about groping women without consent. Following the video's release on Friday, numerous Republican lawmakers said they would not back Trump, though Ryan and Senate Majority Leader Mitch McConnell have not explicitly rescinded their support. Ryan previously pulled Trump's invitation to a campaign event in Wisconsin over the weekend.
A Trump campaign spokesman said in a tweet that "nothing's changed" after the call, saying "a grassroots movement, not Washington" has powered Trump's campaign.
Clinton's campaign responded Monday by tweeting that "Ryan is still endorsing Trump."
The fallout from the leaked video fueled speculation that the Republican Party could pull back on resources to help elect Trump, instead focusing on keeping congressional majorities. Association with Trump could be seen as toxic for some Republicans in tight congressional races.
But Trump's frequent and aggressive appeals in Sunday night's debate to the supporters who fueled his unlikely political rise only complicated matters for candidates who want to keep their distance from him.
The Democratic Party has a chance of taking control of the Senate on Nov. 8, but the GOP is expected to maintain its majority in the House.
— NBC News contributed to this report.