Bill Kristol, anti-Trump activist and editor-at-large of The Weekly Standard, set his sights Wednesday on finding a Republican to challenge President Donald Trump in 2020. Kristol attempted to convince New Hampshire activists that primarying a sitting president is possible.

“I have a feeling that we are now entering … a turbulent era, when the character of both parties is up for grabs,” Kristol told activists at Saint Anselm College over breakfast.

The Weekly Standard editor floated five potential #NeverTrump candidates in an interview with BuzzFeed News’s Henry J. Gomez.

Kristol mentioned former Massachusetts Governor Mitt Romney, Sen. Ben Sasse (R-Neb.), Defense Secretary James Mattis — all three of whom were on his 2016 wish list — and U.S. Ambassador to the United Nations Nikki Haley. Kristol also praised Gov. John Kasich (R-Ohio), whom the Weekly Standard editor visited in Ohio earlier this month.

Very interesting, lively and wide-ranging conversation over dinner here in Columbus with @JohnKasich. What topics did we cover and what conclusions did we draw?

Silentium est aurum. pic.twitter.com/C3rAcmWPCm — Bill Kristol (@BillKristol) May 3, 2018

Of these five, Kasich alone is likely to seriously consider a 2020 run. While Romney and Sasse spoke out strongly against Trump in the past, neither has made moves to suggest a potential 2020 run.

Kristol admitted that Kasich is the most likely to challenge the president. In March, the Ohio governor told The Weekly Standard that he “is increasingly open to the possibility of running for president in 2020 as an independent.”

“It’s possible to say, ‘Yeah, I approve of Trump — maybe not strongly, but somewhat — but I’d also like to have a choice … in 2020 that’s different from Trump,'” Kristol told the audience on Wednesday. “You don’t have to be a Never Trumper to not be on board for eight years of Trump.”

The Weekly Standard editor admitted that challenges to sitting presidents tend to weaken the party in power. In 1968, Eugene McCarthy and Bobby Kennedy challenged then-president Lyndon Johnson, and Richard Nixon got elected that November. In 1976, Ronald Reagan ran a powerful campaign to unseat then-president Gerald Ford, but Jimmy Carter prevailed in the general election. In 1980, Ted Kennedy faced off against Carter, helping the Reagan Revolution succeed.

Even so, Kristol noted that 38 percent of Republican voters said they wanted to see Trump face a primary challenge in 2020, according to a Morning Consult poll. A January poll found that a whopping 82 percent of Republicans between the ages of 18 and 24 wanted Trump to face a primary challenge.

While many Republicans want to see Trump fight for the nomination, it seems unlikely any one candidate could pose a serious threat. Only Sen. Ted Cruz (R-Texas) posed a serious threat in the 2016 primary, and Cruz has largely supported the president, even endorsing him before the general election. Kasich defeated Trump in his home state of Ohio, but he took a distant third in the primary overall.

Kristol sought a #NeverTrump candidate in 2016, and settled on Evan McMullin, a CIA counterterrorist spy with no elected experience. McMullin only contested a few states, and he only received 728,830 votes, taking fifth behind Trump’s 63 million, Clinton’s 65 million, Libertarian Gary Johnson’s 4.5 million, and Green Party candidate Jill Stein’s 1.5 million. In other words, #NeverTrump flopped, hard.

Politics in the age of Trump is notoriously unpredictable, but even if a #NeverTrump candidate emerges for 2020, all bets should be on the president. As for Kristol, he could actually see himself running against Trump — but only “if no one else runs.” Even then, he would try to enlist someone else.