Libertarian presidential nominee Gary Johnson said House Speaker Paul Ryan (R-Wis.) can still say he made a mistake in endorsing Donald Trump, even if that doesn't mean getting behind the Libertarian ticket. 

"It's too bad that Paul Ryan has really stuck his neck out, if you will, in endorsing Donald Trump," Johnson said in an interview with CNN to air Sunday.

Johnson pointed out that Ryan has had to distance himself from many of the presumptive GOP presidential nominee's comments — most recently his ban on Muslim immigration. 

"I think Paul Ryan has an opportunity here to say, 'Look, I made a mistake.' I’m not saying that results in an endorsement of me, but come on, the statements that he’s making — he’s made 100 statements that would disqualify any other presidential candidate from running, and yet all you have to do is turn the page and tomorrow it will be 102."

CNN anchor Erin Burnett asked Johnson about a past interview with 2012 GOP presidential nominee Mitt Romney, in which he said he would consider voting libertarian. 

"He echoes the sentiment of a lot of Republicans, and I think it's also the sentiment among a lot of Democrats," Johnson said.

But Romney has his reservations — including Johnson's support of legalizing marijuana. Romney argued against legalization and said that marijuana "makes people stupid." 

"I do not agree with that," Johnson said. "As someone who has used marijuana, I do not agree with that."