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Sen. Marco Rubio told the nation’s largest annual gathering of political conservatives that the next elected president must be more committed to strengthening the military, protecting gun ownership rights as well as religious freedom.

“What kind of country is this going to be in the 21st Century?” said Rubio, a Florida Republican who is running for president, adding that voters must not allow the election and the country to be “hijacked by someone who is not a conservative.”

That reference to billionaire and GOP frontrunner Donald Trump, whom Rubio did not name, got the loudest cheers and a standing ovation by the crowd of thousands at the Conservative Political Action Conference, or CPAC, on Saturday.

Many attendees at CPAC already were feeling negative about Trump, who abruptly cancelled plans to speak at the conference, where he was scheduled to appear at 8:30 a.m. Saturday. The Trump camp said they had scheduling conflicts.

Asked about Trump’s no-show by CNN’s Dana Bash after his speech, Rubio said the conference is “usually reserved for conservatives,” drawing loud applause from the crowd.

Rubio often has said that Trump is not a conservative because of, among other things, the mogul’s defense of the non-abortion services that Planned Parenthood provides.

Rubio, who has sounded hoarse in appearances – including Thursday’s GOP debate on Fox News – this week, told the crowd he has been battling the flu, and held up a Poland Springs water bottle and took several drinks.

In his speech, Rubio said “For over two decades leaders in neither party have solved the problems before us.”

“Neither anger nor fear will solve our problems,” he said. “It can serve to motivate us, but it will not solve our problems.”

Rubio made many references to the importance of his religious faith, spoke against abortion and said “Our rights come from God.”

Time and again, Rubio cast himself as a true conservative.

“What does it mean to be a conservative in the 21st Century?” he asked. “It can never be about simply an attitude…about how long you’re willing to scream…or how many names you’re willing to call people.”

“Conservatism has never been about fear or about anger, not at its best.”

He added that anger and fear “can serve to motivate us, but it will not solve our problems.

Rubio said he walked through the kitchen of the convention center to make his way to the ballroom where he was speaking, and stopped to speak to the workers “who are doing the jobs that my parents once did.”

Rubio received thunderous applause through his speech, and during his responses to Bash’s questions. The day before, his rival, Sen. Ted Cruz, of Texas, also got a rock-star reception. But the crowd seemed more awed by Rubio.

Rubio was scheduled to go to Jacksonville, Florida after CPAC to campaign with New Mexico Gov. Susana Martinez, who in recent days announced her endorsement of him. Then he was heading to Puerto Rico, where a win in Sunday's primary could help him lock up support in Florida.

Rubio reserved most of his criticism at Trump without naming him.

He said: “The American Dream is not about how many buildings have your name on it.”

It’s a crucial time in Rubio’s campaign, having won just one state in the GOP primaries while his main competitors, Cruz and Trump have won more.

Trump leads the pack with the most states won and, by extension, the most delegates with 336, Cruz follows with four states and 231 delegates.

Rubio won Minnesota during Super Tuesday, and has 110 delegates.

Ohio Gov. John Kasich has 25 delegates, and says he will stay in the race at least until the March 15 primary in his state.

Rubio must win his state of Florida, whose primary also is March 15, to be seen as a true competitor to Trump, political experts say.

A Republican candidate must get 1,237 delegates to be the nominee.

Rubio told Bash that despite polls projecting Trump will win Florida, he is confident he will win. He said when he ran for Senate, all indications were he would not win, but he did.

He also said he has no hard feelings toward his former mentor, Florida Gov. Jeb Bush, who dropped out of the presidential race after a poor showing in New Hampshire and polling poorly.

He said he has spoken to Bush since then and considers him the best governor in the history of Florida.