President Donald Trump just threw the proverbial gauntlet down in front of his 2016 Democratic opponent, Hillary Clinton, today.

Trump took to twitter and called  Clinton “the worst (and biggest) loser of all time,” in a tweet, adding, “She just can’t stop, which is so good for the Republican Party. Hillary, get on with your life and give it another try in three years!”

Crooked Hillary Clinton is the worst (and biggest) loser of all time. She just can’t stop, which is so good for the Republican Party. Hillary, get on with your life and give it another try in three years!

— Donald J. Trump (@realDonaldTrump) November 18, 2017

The tweet was likely in response to Clinton’s attack on Trump, telling him to take responsibility for the sexual assault allegations leveled at him, while applauding Al Franken’s response to sexual assault allegations against him.

“I don’t hear that from Roy Moore or Donald Trump,” Clinton said during a Friday interview. “Look at the contrast between Al Franken, accepting responsibility, apologizing, and Roy Moore and Donald Trump who have done neither.”

Both Clinton and Trump have been in a back and forth since his election. Trump has recently pushed for Clinton to be investigated by the Justice Department for her, and the Clinton Foundation’s part in the Uranium One scandal, which saw Clinton’s State Department okay the sale of an American uranium company to Russia in 2010.

Clinton in return has called this potential investigation an “abuse of power.”

Despite Trump’s 2020 challenge to Clinton, Clinton says she’s done with being a political official and will not be running again.

At this time, Trump’s main 2020 opponents look to be Bernie Sanders, currently the politician with the highest approval rating, and former Vice President Joe Biden who is already 11 points ahead in the 2020 polls.