President Trump's three primary challengers are blasting the Republican Party for taking a "wrong turn" by embracing a "serial self-promoter who has abandoned the bedrock principles of the GOP."

In a joint op-ed published by the Washington Post Friday, former South Carolina Gov. Mark Sanford, former Massachusetts Gov. Bill Weld, and former Illinois Rep. Joe Walsh express their "shared conviction that the United States needs a strong center-right party guided by basic values that are rooted in the best of the American spirit."

The trio lambasted the Trump era for ushering in "a preference for alienating our allies while embracing terrorists and dictators, attacking the free press and pitting everyday Americans against one another" while abandoning "personal responsibility, fiscal sanity and rule of law." Then, they turned their criticism toward Team Trump's "latest disgrace," the recent move by the Republican parties in four states, including Arizona, Kansas, Nevada, and South Carolina, to cancel their 2020 primaries and caucuses.

"What does this say about the Republican Party?" they asked. "If a party stands for nothing but reelection, it indeed stands for nothing. Our next nominee must compete in the marketplace of ideas, values and leadership. Each of us believes we can best lead the party. So does the incumbent. Let us each take our case to the public."

Sanford, Weld, and Walsh pointed out that Democrats, on the other hand, "are still engaged in a heated competition of debates, caucuses and primaries to give their voters in every corner of our country a chance to select the best nominee" and wondered why Republicans aren't doing the same across the nation.

"Do Republicans really want to be the party with a nominating process that more resembles Russia or China than our American tradition?" the mulled. "Under this president, the meaning of truth has been challenged as never before. Do we as Republicans accept all this as inevitable? Are we to leave it to the Democrats to make the case for principles and values that, a few years ago, every Republican would have agreed formed the foundations of our party?"

The president's challengers called it a "critical mistake" by the GOP to let Democrats "dominate the national conversation during primary and caucus season" and made their case as to why they should be allowed to "take our message to the public and prove we are right." They also dismissed the claims by Republican state parties that money would be wasted on holding primaries and caucuses because Trump "will win by a landslide."

"Since when do we use poll numbers as our basis for deciding whether to give voters an opportunity to choose their leaders, much less their presidents? Answer: We don’t," they wrote, adding that the litigation costs the four states will have to pay to defend legal challenges to their cancellations "will almost certainly exceed the cost of holding the primaries and caucuses themselves."

"In the United States, citizens choose their leaders," they concluded. "The primary nomination process is the only opportunity for Republicans to have a voice in deciding who will represent our party. Let those voices be heard."

The op-ed comes after Arizona, Kansas, Nevada, and South Carolina canceled their primaries and caucuses for the 2020 presidential election. Walsh and Weld slammed the decision at the time, calling it "undemocratic bull." The Trump campaign, however, pushed back on the uproar, saying it's "nothing that hasn't happened with both parties when you have an incumbent president on the ballot."