WASHINGTON (AP) — The three Republican challengers to President Donald Trump say it's a mistake for the party to cancel primaries ahead of the 2020 election.

Bill Weld, Joe Walsh and Mark Sanford write in a Washington Post opinion piece published Friday that the Republican Party has "taken a wrong turn" in letting Trump define the party. They describe the president as "a serial self-promoter who has abandoned the bedrock principles of the GOP."

At least four states — South Carolina, Nevada, Arizona and Kansas — have canceled Republican primaries and caucuses next year to help smooth Trump's path to reelection. Weld, Walsh and Sanford are urging the party to reconsider.

Trump has dubbed his three challengers "The Three Stooges." None of them is expected to generate enough support to defeat Trump.