Donald Trump may, or at least should, face sharp questioning from two separate quarters in Tuesday night's Republican debate in Las Vegas. His opposing candidates need to target him to salvage their own campaigns, and the CNN moderators need to expose his demagoguery for the sake of the political process' own reputation.
None of the other 13 declared candidates has been able to gain comparable traction in the major public-opinion polls. As a result, Mr. Trump's domination of the Republican Party has brought its establishment, represented by center-right and moderate sentiment, to a near-apoplectic state.
The fear among these old bulwarks of the Ronald Reagan and senior George Bush administrations is that the ultraconservatism that has increasingly asserted itself in the GOP ranks has found its savior in Mr. Trump — or he has found his political salvation in it.
While Trump enthusiasts have seized on him as their authentic voice, other party loyalists see him as a certain loser in the 2016 general election, or as a potential third-party spoiler if somehow he is denied the nomination.
For all of Trump's earlier divisive racial and anti-immigrant taunts, he outdid himself recently with his declaration that he would bar all Muslims from U.S. entry. Though it did stir some of his 2016 rivals like Jeb Bush, John Kasich, Lindsey Graham and Chris Christie to voice their dissent, they fell short of saying they would not support him if nominated. Mr. Kasich, for one, clung to the conviction that it will not happen.
As a group, they seemed unwilling or unable to take any strong and open stand against Mr. Trump in defense of their party and its basic tenets, which obviously include freedom of religion and that there be no religious test for participation in Republican ranks.
Of the other surviving GOP presidential candidates, only Sen. Ted Cruz of Texas, who is offering himself as a sort of Trump Lite of less offensive personal bombast, appears to see the Trump phenomenon as a potential source of strength to himself, and a transformation of the soul of the GOP.
Mr. Cruz, like Mr. Trump, is willing to ride the whirlwind of racial hatred and bitter nativism whipped up by recent Islamic terrorism. He is playing it as a political card to cast himself as the muscular man of the hour that the threat calls for. He, like Mr. Trump, offers himself as the Republican antidote to the cautious Democratic president in the Oval Office.
So it may also depend on the CNN moderators of the Tuesday-night debate to hold Mr. Trump's feet to the fire on his latest outrageous scheme to make all Muslims persona non grata here. They include Wolf Blitzer, host of CNN's daily "Situation Room," CNN congressional and political correspondent Dana Bash, and Hugh Hewitt of Salem Radio Network, a conservative commentator — hardly akin to a medieval star chamber.
Seven carryover candidates from the last Republican debate — Sens. Ted Cruz, Marco Rubio and Rand Paul; Ohio Gov. John Kasich; Jeb Bush, Ben Carson and Carly Fiorina, plus New Jersey Gov. Chris Christie, are expected to join Mr. Trump in the main event. Four others — South Carolina Sen. Lindsey Graham, former governors Mike Huckabee of Arkansas and George Pataki of New York, and former Pennsylvania Sen. Rick Santorum — are expected to be on the earlier undercard. Their participation will be determined by their polling numbers in advance of the approaching Iowa precinct caucuses and New Hampshire primary in February.
Beyond refereeing among the presidential candidates appearing with Mr. Trump, the moderators should encourage all participants to examine how the Trump phenomenon has affected the reputation and credibility of the Republican Party, beyond their personal interest in their own chances to be nominated.
Obviously, such a discussion would make Mr. Trump once again the central figure. But it also might well oblige the candidates, and viewing voters, to consider more seriously how the current circus is diminishing respect and admiration for one of the two great parties in American political history. Mr. Trump's bigoted world is not where the party of Lincoln or any of his successors should want to take us.
Jules Witcover is a syndicated columnist and former long-time writer for The Baltimore Sun. His latest book is "The American Vice Presidency: From Irrelevance to Power" (Smithsonian Books). His email is firstname.lastname@example.org.