Marco Rubio, then the junior United States senator from Florida, formally announced his 2016 presidential campaign on April 13, 2015, at the Freedom Tower in Downtown Miami.

[4] Rubio was the second Cuban American to run for president, with Republican Ted Cruz announcing his campaign three weeks earlier.

[6] Despite his comments, speculation continued that presidential candidate Mitt Romney might select Rubio as his running mate.

[7] According to the book Double Down, Romney's campaign narrowed down his list of potential nominees for vice president to five candidates, one of which was Rubio.

Groups supporting Rubio raised over $530,000 in the first three months of 2014, most of which was spent on consultants and data analytics, in what was seen as preparations for a presidential campaign.

[24][25][26] A poll from the WMUR/University, tracking New Hampshire Republican primary voters' sentiment, showed Rubio at the top alongside Kentucky senator Rand Paul in March 2013.

He began contacting top donors and appointed advisors, including George Seay, who previously worked on Rick Perry's 2012 presidential campaign and Mitt Romney's 2008 presidential campaign, and Jim Rubright, who had previously worked for Jeb Bush, Romney, and John McCain.

[32][33] Rubio also instructed his aides to "prepare for a presidential campaign" prior to a Team Marco 2016 fundraising meeting in South Beach.

Over the course of both of the first two debates, in August and September, Rubio was widely praised as one of the top performers, even being called the winner by some analysts.

[51] Rubio, along with Paul Ryan and his recent ascension to the House speakership, Lewis says, means "both men will be attacked for their youth and energy", adding: "But it's hard to look at this strong and diverse Republican bench, and not juxtapose it to the Democrats, whose party – now that Barack Obama is a lame duck – seems to be represented by a bunch of old white people, such as Hillary Clinton, 68, Bernie Sanders, the 74-year-old democratic socialist candidate, ...Nancy Pelosi, 75, and Harry Reid, 75... For Democrats, who were hoping they would get to deal with old pols like John Boehner and Jeb Bush...the world just got a little bit scarier".

On December 29, Rubio responded to Christie by claiming to have close to a 90% attendance record while also retorting that the governor had "been missing in New Jersey half of the time.

[63] A little over a week after the primary, on February 10, Rubio accused Cruz of having misled voters through claiming fellow candidate Ben Carson would be ending his campaign in what he called "a concerted effort that I'm sure they planned to execute on something in order to influence the election.

[66] Rubio defended these remarks the following day, saying with respect to the statement that Obama "knows exactly what he's doing" that "It's what I believe and it's what I'm going to continue to say, because it happens to be one of the main reasons why I am running.

Shortly afterward, Rubio admitted to supporters that he was disappointed and concluded that his debate performance three days prior had not helped him in the state.

[79] The next voting state, Nevada, was seen as one that Rubio could potentially claim as his first victory due to the outpouring of support from the Republican Party.

Some commentators observed Rubio having spent six years of his childhood in the state as a potential advantage over the other candidates in appealing to voters.

Nevada lieutenant governor Mark Hutchison publicly expressed confidence in Rubio's chances, as did the candidate himself.

Following the second-place finish, aides of Rubio said he would only win if supporters of both Kasich, who was still running despite poor performances in nearly every one of the four states, and Bush coalesced behind him.

[90][91] The following day, Rubio withdrew from planned appearances in Kentucky and Louisiana that were scheduled in the latter part of the week, leading to speculation that the move was the result of a lack of confidence the Rubio campaign had in its chances to win the two states, polling at the time showing Trump in first place.

[92] On March 6, Rubio had won the Puerto Rico Republican primary by a large margin, pulling in 71.02% of the vote.

[93] Rubio previously addressed Puerto Rico during a CNN debate, arguing that its problems stemmed from an economy that was not growing and that it was "too expensive to do business there."

[105] On the day of the Florida primary, Rubio said that his campaign would continue to Utah regardless of the results and charged the polls, all of which showing him behind Trump, as being "out of control.

"[106] On March 15, 2016, Rubio suspended his campaign, when he finished second in the primary of his home state of Florida held that day.