Donald Trump hasn't had many nice things to say about Hillary Clinton lately, but the GOP frontrunner said Monday it would be an "amazing thing" if the two faced off in the November election.

"It's going to be interesting to see what happens. I think it's going to be one of the most interesting races," Trump told Jimmy Fallon during "The Tonight Show" taping Monday afternoon. "A poll came out, if I win (the Republican nomination) and she wins (the Democratic nomination), it's going to be the largest voter turnout in the history of the country."

Trump went on to tell Fallon that if that happens it'll be an "amazing thing" because "people don't vote that much in this country."

Fallon then asked Trump about a conspiracy theory that Trump is actually a plant of the Democratic Party set up to help Clinton win.

"Well, I mean they like to start that," Trump said to a laughing audience.

Last week Trump lobbied attacks against Clinton and former president Bill Clinton.

"I haven't even started on her yet, although last week I did a little bit. But we haven't even started," Trump told Fallon.

Monday night was Trump's second appearance on the NBC late night broadcast since he began his presidential campaign in June.

Related: Hillary Clinton to be on 'Tonight Show' same week as Donald Trump

On Thursday, Clinton will have her turn with Fallon, marking her second guest spot on the show during the campaign season.

Presidential candidates have been appearing regularly on late night telecasts in recent months.

With the Iowa caucuses on February 1 and the New Hampshire primary on February 9, the late night landscape may become even more populated with candidates in the coming weeks.