During Wednesday night’s Democratic town hall in New Hampshire, Sanders told CNN moderator Anderson Cooper that he hopes that Donald Trump wins the Republican nomination. “Frankly, I’m prejudiced,” Sanders said. “I want Trump to win the nomination. I would love the opportunity to run against him. I think we would win by a lot.”

In the Iowa Caucuses on Monday, the Vermont senator lost to Hillary Clinton by a sliver—49.9% vs. 49.6%—while Donald Trump got 24.3% of the Republican caucus, putting him second to Ted Cruz, with 27.7%.

Trump wasn’t so flattered by Sanders’ attention:

Sanders says he wants to run against me because he doesn't want to run against me. He would be so easy to beat!

— Donald J. Trump (@realDonaldTrump) February 4, 2016

Sanders also had some fun with the billionaire’s denial of climate change after Cooper asked him to compare himself to Trump. “Trump is, as you know, a well-known scientist—brilliant scientist. He has concluded after years of studying the issue that climate change is a hoax brought to us by the Chinese,” Sanders said. “Now, that shocked me because I thought it was a hoax brought to us by the Mexicans or the Muslims.”

Fortune has contacted the Trump campaign for comment and will update this story if it responds.