Republicans are barreling toward Super Tuesday with another debate in the offing and Donald Trump’s opponents reaching for perhaps their last best chance to knock him off stride for the presidential nomination.

Expect a nasty turn, Trump warned, as if the roiling GOP race were anything but that already.

The New York billionaire predicted that the relative civility between Marco Rubio and himself would fall away in the frantic grasp for hundreds of convention delegates in the 11 states that hold Republican primaries Tuesday.

Even John Kasich, a trailing contender whose calling card has been a positive campaign, went sharply negative Wednesday in a campaign broadside against Rubio, the Florida senator who is soaking up Republican establishment support and thereby threatening to starve Kasich’s effort of its remaining oxygen.

Trump exercised bragging rights with trademark gusto after Nevada handed him his third straight victory the night before.

Relaxed on stage at Virginia’s Regent University, Trump fielded questions from Christian conservative figure Pat Robertson, ticking off Obama administration executive orders he wants to reverse as president and joking about his recent dustup with the pope.

He said earlier he might tone down his contentious rhetoric if he makes it to the White House — or not, since “right now it seems to be working pretty well.”

And what of Rubio?

“So far he’s been very nice and I think I’ve been very nice to him,” Trump said on NBC’s “Today” show. “We haven’t been in that mode yet but probably it’ll happen.” He meant attack mode.

On the Democratic side, Hillary Clinton scored the endorsement of Nevada’s Harry Reid, the party’s Senate leader, in advance of a primary Saturday in South Carolina, where she looks strong. She prevailed in the Nevada Democratic caucuses days before the GOP contest there, dulling rival Bernie Sanders’ drive and making Super Tuesday of crucial importance to him.

On Tuesday:

—Republicans will award 595 delegates in 11 state races, with 1,237 delegates needed to clinch the nomination.

—Democrats will award 865 delegates in 11 states and American Samoa, with 2,383 needed for the nomination.

The election calendar suggests that if Trump’s rivals don’t slow him by mid-March, they may not ever. Delegate totals so far: 82 for Trump, 17 for Ted Cruz, 16 for Rubio, 6 for Kasich and 4 for Ben Carson.

For Republicans, Nevada offered little evidence Republicans are ready to unite behind one strong alternative to Trump, who many in the party fear is too much of a loose cannon to win in November.

Mainstream Republicans who don’t like Trump are also in large measure cool on Cruz. With Jeb Bush out of the race and time short, they have begun gravitating to Rubio, long a man of promise in the race but one who has yet to score a victory.

The Florida senator edged Cruz, a Texas senator, for second place in Nevada, and it’s clear his time is at hand — if he’s to have one.

With Bush gone, the GOP debates have lost a prime Trump critic, though Cruz has been a fierce antagonist at times and Rubio faces pressure to confront the billionaire more directly before it’s too late.

Their debate Thursday night is in Texas, the largest of the Super Tuesday states and one where Cruz has an advantage as home-state senator.

Trump’s provocative proposals to build a massive border wall with Mexico and to deport all people in the country illegally are sure to feature in the debate, which has Spanish-language Telemundo as a partner with CNN.

Trump is just as certain to brag about winning the largest share of Hispanic votes in Nevada, among the limited numbers of Latinos who participated in the Republican caucuses.

Cruz, a fiery conservative popular among voters on the GOP’s right, won the leadoff Iowa caucuses but underperformed in South Carolina and Nevada. He’s recently been on the defensive for his campaign’s sharp-elbowed tactics and in the face of withering criticism by Trump of his integrity.

(AP)