WASHINGTON — Marco Rubio unleashed a campaign’s worth of harsh criticism on Donald Trump in the final Republican debate before Tuesday’s crucial primaries.

The problem may be that it took 10 debates and three Trump victories to get Rubio fired up.

Rubio, along with most of the other GOP presidential candidates, has treated Trump with kid-gloves, tiptoeing around glaring questions about the mogul’s business record, political ideology, brash temperament and ambiguous policy proposals.

Only now, with Trump threatening to pull away from the field, did Rubio aggressively try to dismantle the billionaire businessman’s grip on the Republican race, with occasional help from Texas Sen. Ted Cruz.

Rubio accused Trump of shifting his position on deportation and staffing his hotels and other businesses with foreign workers instead of Americans. He also punched holes in the real estate mogul’s vague proposal for replacing President Barack Obama’s health care law. “What is your plan, Mr. Trump? What is your plan on health care?” Rubio pressed.

The senator also gleefully pointed out Trump’s propensity for repeating talking points over and over again, the same criticism that tripped up Rubio in a debate earlier this month.

“Now he’s repeating himself!” Rubio exclaimed.

Rubio’s assertive posture was sure to be cheered by the crush of Republican officials who have rallied around his campaign in recent days, desperate for the senator to become a viable alternative to Trump. But privately, many were likely wondering why it took so long for Rubio to make his move — and whether his strong showing came too late.

Next week’s Super Tuesday contests mark the biggest single-day delegate haul of the nomination contests. A strong showing by Trump could put the nomination within his grasp, raising the stakes for his rivals to stop him.

Rubio was sometimes joined by Cruz in tag-team attacks on Trump. It was a tactical shift for two senators who had trained their fire on each other in recent weeks, both betting that the best strategy was to clear the field of other rivals before moving on to Trump.

But Tuesday’s Nevada caucuses clearly changed their calculus. Trump dominated that contest, beating second-place Rubio by more than 20 points, and pulling ahead significantly in the early delegate count after victories in South Carolina and New Hampshire as well.

Trump appeared rattled as he faced the most sustained, face-to-face attacks of the campaign. Before Thursday, only Jeb Bush had made a real effort to tangle with Trump on the stage, though it did little to help the former Florida governor. Bush ended his campaign last week.

Rubio’s next challenge — beyond topping Trump in at least some of the upcoming primaries — will be infusing that more optimistic message into his critique of Trump. He’s also likely to face the full force of Trump’s attacks for the first time in the campaign.

Trump suggested he was eager to keep up the fight.

“This is a lot of fun up here, I have to tell you,” Trump said.