The first 52 minutes of the tenth GOP presidential debate focused on one topic, immigration, and offered us the most explosive fights that we have seen in any of the presidential debates so far. In short, it was the debate that we as Republicans have long deserved.

Using multiple parries, Marco Rubio showed us that he is a dynamic and quick-thinking candidate with a mastery of the debate stage. Senator Rubio changed his approach to Donald Trump and took him on directly. The result? He did what no other candidate has been able to do in this election season; he got under Trump’s skin and exposed him as the lightweight that he is.

First, Rubio hit Trump for his use of foreign workers at his many properties. He then made the crack that Trump’s border wall with Mexico would probably be built by foreign workers too. Trump smirked and turned red.

Next, Trump was hit by Rubio over how he is not a good businessman with the stinging line, “If you hadn’t inherited $200 million, you’d be selling selling watches on the streets of Manhattan.” Trump’s response? He muttered how his father only gave him $1 million. The audience was stunned.

Then came the exchange of the night. Rubio sought to highlight how Trump’s plans are lacking substance, specifically his healthcare “plan.” Trump explained that he would eliminate “lines” that prevent some insurance companies from competing in other states. Rubio pounced. He asked Trump for other aspects of his plan and all Trump could do was repeat his answer about “lines.” With a wry grin, Rubio then accused Trump of repeating himself.

Trump, knocked back on his heels, sputtered, “I don’t repeat myself. I don’t repeat myself.” Ironic. Still flustered, Trump then said, “I saw this guy repeat himself five times a month ago.”

Without missing a beat, Rubio fired back, “I saw you repeat yourself five times five seconds ago.” The audience went wild.

Rubio’s night was not just good because of his willingness to take on Trump, but because of the rest of his answers. On Apple’s refusal to comply with the federal court order to unlock the San Bernardino shooter’s iPhone, “Apple’s brand is not superior to the national security of the United States of America.” He deftly handled the question of the Puerto Rican debt crisis. Rubio took on President Obama’s illegal use of executive orders on immigration. From start to finish, Rubio’s performance was a master class in presidential debating.

Trump’s night was obviously not as good as Rubio’s. In fact, it was the polar opposite. He was on the defensive on his record (accusations of fraud against Trump University and shady business practices), his love affair with Hillary Clinton, his refusal to release his tax returns (Trump can’t release them because the IRS is auditing him— begs the question of what are his tax returns hiding?) and his questionable support for Israel. But does that matter to his supporters? Nope. Come hell or high water, they are determined to support Trump no matter what.

The important question that needs to be asked is if tonight helped Marco Rubio? Without a doubt it did. His willingness to fight Donald Trump, not the other candidates, at every appropriate turn showed that he is the candidate who can take on Hillary Clinton in November.

Over the summer, Trump’s supporters constantly rebuffed people who highlighted shortcomings in the Trump record, with the refrain, “but he fights.” Now, Marco Rubio has demonstrated that not only can he fight, but he can land a mean right hook, but he can do so without seeming angry or foaming at the mouth.

Tonight’s debate performance was one of the final chances for Republican primary voters who do not support Donald trump (roughly 60 percent of the GOP) to look for a true alternative to him. They know that Donald Trump would be a disaster for the Republican Party’s electoral chances in November. They know that Donald Trump lacks the temperament and judgment to be president. They know that Donald Trump has no grasp of complex policy and the problems that impact the daily lives of Americans. They know that making deals is not how you stop ISIS. They know that Donald Trump is in no way suited for the presidency.

Now, they know that Marco Rubio is the clear alternative to Donald Trump.