Sen. Marco Rubio (R-Fla.) with Kansas Gov. Sam Brownback at a campaign rally Friday in Topeka. (Paul Sancya/AP)

Sen. Marco Rubio vowed again Friday that he will win his home state of Florida and said Republicans should be preparing for a protracted delegate fight.

Trump leads Rubio in polls released in the past few days, and Rubio is preparing to barnstorm the Sunshine State starting Sunday. The goal is to rob Trump of the state's 99 delegates, which will be awarded on March 15 in a winner-take-all contest.

Winning in Florida, Rubio said, will be "a huge bump for our campaign and a huge loss for everybody else."

Rubio, Sen. Ted Cruz of Texas and Ohio Gov. John Kasich are now hoping to at least slow Trump's ability to amass the nearly 1,300 delegates needed to win the Republican nomination. Cruz won his home state of Texas, and Kasich is hoping to win the Buckeye State on March 15. Kasich has vowed to drop out of the race if he loses Ohio, but Rubio declined to take such a pledge Friday.

"No, because we're going to win Florida — we're very confident about that. We're prepared for a campaign that goes beyond Florida, as well," he said.

With Cruz and Kasich still in the race, "this is going to be a protracted deal here," Rubio said, "but I feel very good about the states that are coming up."

"It's been a very unusual political year. As I've said, there's a core of the voters that don't want Donald Trump — the vast majority do not want Donald Trump to be our nominee," he added. "But those votes are still being divided up between two or three people and other names that are on these ballots. So it's made it harder to coalesce. So we're going to continue to work hard to get as many of those votes as possible. I can tell you we'll leave here tomorrow with delegates, and this has now become a delegate fight to see who can get to 1,237 first. And if not, who can go into the convention with the highest number of delegates."

The Rubio campaign is moving staffers from earlier contests into Florida this weekend to help prepare for the senator to crisscross his state in the next nine days and to turn out voters. But already nearly 500,000 Floridians have voted early or cast absentee ballots, meaning Rubio has probably missed an opportunity to convince hundreds of thousands of potential supporters.

In the lead-up to the primary, Rubio is expected to focus especially on his native South Florida — packed with a high percentage of Republicans who, like the senator, are of Cuban descent. He'll also pay close attention to military-heavy communities around Pensacola in the Panhandle and to the "I-4 corridor" that stretches from Tampa east to Orlando and on to Daytona Beach along Interstate 4. The region is packed with swing voters, including a growing percentage of Puerto Rican immigrants, many of whom are registered Republicans but whose political allegiance otherwise remains up for grabs.

With roughly $5 million on hand as of February, the Rubio campaign is relying on outside groups to spend millions of dollars on television advertising. Three super PACs — Conservative Solutions PAC, Our Principles PAC and a group launched by the Club for Growth — are now spending more than $10 million combined on ads attacking Trump.

Rubio warned on Friday that the Sunshine State primary is "going to be close."

"Look, Florida is a very competitive state. And there's a lot of people that live in Florida, that vote in Florida, but don't live there year round," he said. "So it's a unique state in that regard. So it's going to be close, especially with something like Donald Trump going on and the amount of national attention he's gotten."

The senator spoke with reporters in Topeka, Kan., in one of his most expansive exchanges with the press in several days. He was also stopping Friday in Wichita and Overland Park, outside Kansas City. Kansas holds a GOP caucus on Saturday, while Missouri votes on March 15.

On Saturday, Rubio is scheduled to address the Conservative Political Action Conference outside Washington before rallying with supporters later in the day in Jacksonville and Puerto Rico, which holds a primary Sunday. Rubio is poised to win the island's 23 delegates, which would be a healthy injection of support.

Despite its commonwealth status and the existence of island-specific political parties, Puerto Rico participates in the party primaries and sends delegates to the Democratic and Republican party nominating conventions.

Reporters pressed Rubio to explain why, after attacking him relentlessly during Thursday night's debate, he agreed to support Trump if he wins the GOP nomination.

"Because that's how bad Hillary Clinton is," he said. "That's what we're trying to avoid — the fact that you're even asking this question about the supposed front-runner, the fact that we keep getting asked, 'Will you vote for the front-runner?' as Republicans, shows you how flawed a candidate he is."

He criticized Trump's "constant movement" on issues, particularly immigration, accusing his opponent for flip-flopping on Thursday night on the issue of allowing immigrant workers to enter the country.

"It's just a pattern, and it's disrespectful to the voter, but I think it indicates that this is a person who has spent zero time thinking about public policy," he said.

"And there's a reason you're seeing this, guys. Donald Trump has spent his entire business career convincing people that he is something that he is not," he added. "And usually it was for the purposes of getting them to part with their money. Now he's doing it for purposes of getting people to give him his votes so he can take control of the country. This is a very sad situation to watch unfolding now in the Republican Party, and we still have time to prevent it."

Trump announced on Friday that he will be skipping CPAC, usually a must-attend event for Republicans seeking the presidency. Rubio said the reason Trump isn't attending is that, on issue after issue, "he really doesn't belong at a conservative gathering. Donald Trump is not conservative."

Rubio's stops in Kansas were hastily arranged this week and led to the cancellation of planned visits to Kentucky and Louisiana, which vote on Saturday. Rubio sought Friday to play down suggestions that the change in schedule signaled turmoil in his campaign.

"It's a question of where we can get to in time to do visits. We have teams in Michigan. We have teams tomorrow in Kentucky. We have teams in Louisiana," he said. "We have a campaign in virtually all 50 states and in every territory. It's just a question of, logistically, can you get there in time to do an event or not? And of course, we have a very strong team here. . . . We were able to put some good events together right before the caucus."

Separately Friday, Rubio again called on President Obama to cancel his scheduled trip to Cuba after Secretary of State John F. Kerry scrapped a trip to the island nation amid diplomatic haggling over whether the president will be able to meet with dissidents.

In a statement issued by his Senate office, Rubio said he was "heartened that the administration is even trying to raise issues related to human rights, but the president of the United States, as the leader of the free world, should never have to negotiate the right to meet freedom fighters or raise issues of concern when traveling abroad."

"The Castro regime is not worthy of the honor of a visit by an American president, and the Cuban people deserve better than a continuation of a failed policy that only empowers their oppressors," he added.