WASHINGTON — It's Marco Rubio's version of the Tom Petty anthem I Won't Back Down.
Five weeks after Jeb Bush hurled himself into what looks like an inevitable 2016 campaign for president, Rubio shows no sign he's going to defer to the fellow Floridian and he remains on track to launch his own bid for the Republican nomination.
No one expected Rubio to wave a white flag, but his words and actions are more than keeping up appearances as he promotes a new book that will take him to early primary states. In recent days, Rubio has added muscle to his political staff and will camp out in California next week, skipping out on his job in Washington for a series of fundraisers.
"Prepare for a presidential campaign," Rubio recently told aides as he headed for a weekend huddle with donors in Miami Beach.
Here are some observations from recent weeks:
Rubio has been telling supporters and reporters that his family is on board if he decides to run (he jokes he could see them more if they lived at the White House) and insisting his decision will not be made on what Bush does.
Though subtle, the 43-year-old Rubio implicitly criticizes some of the veterans of the political process, saying the country needs fresh ideas.
He says he can win. Of course he would say that, but it illustrates a strategy aimed at generating news coverage and in turn sending signals to campaign donors and grass roots activists.
"Certainly these races will be very competitive, and there's factors outside of our control that will determine a lot of it," Rubio recently told the Associated Press. "But if we made the decision to run for president, I believe that we can put together the organization and raise the money necessary to win."
Sharpening his argument.
On Wednesday, Rubio offered a counter to the notion that a governor may be better equipped as a candidate, saying governors — Bush, the two-term former governor of Florida, Chris Christie, the current governor of New Jersey, and others in a growing candidate pool of Republicans — will lack the foreign policy experience he has accumulated in the Senate.
"The next president of the United States needs to be someone who has a clear view of what's happening in the world, a clear strategic vision of America's role in it, and a clear tactical plan for how to engage America in global affairs," Rubio told about 40 reporters at a breakfast in Washington hosted by the Christian Science Monitor.
"And I think for governors that's going to be a challenge, at least initially, because they don't deal with foreign policy on a daily basis.
"I've only been in the Senate now for four years and two months, but I've certainly been very engaged in the national security and foreign policy debate," said the member of the Foreign Relations and Intelligence committees. "And I feel very comfortable discussing and debating that with any of the potential candidates."
Continuing to rake in campaign money, invest in staff.
In between media appearances around his book, American Dreams, Rubio has been scooping up campaign cash. He has raised money recently in New York, South Carolina and Alabama and this weekend huddled with "Team Marco 2016" donors in Miami Beach.
Rubio will spend this week in California at a series of fundraisers that will benefit his U.S. Senate re-election campaign (should he decide not to run for president) and his Reclaim America PAC. He has raised millions — with more than $3 million in the bank — pouring a lot into a stable of strategists and advisers, and a grass roots fundraising network.
He just lined up Anna Rogers, who has been finance director for American Crossroads and Crossroads GOP, groups affiliated with strategist Karl Rove, to fill a similar role for his PAC.
He kicks off the California run today at a gathering in Palm Springs put on by the billionaire Koch brothers, leading underwriters of conservative causes and candidates. Rubio will take part in a moderated issues forum with Sens. Ted Cruz of Texas and Rand Paul of Kentucky, both of whom are looking at presidential runs.
Next month, Rubio picks up the book promotion with a tour that will take him to early primary states.
Collectively, the moves highlight someone who believes there is room for him in the race for president.
"I thought it was a ploy to sell books but his potential candidacy seems to be very real as conservatives may see him as the clearer alternative to Jeb and Mitt Romney," Javier Manjarres, a conservative blogger in South Florida, said of Rubio's recent signals.
Noting the lawmaker's trouble with the base over comprehensive immigration reform, he said Rubio has backtracked significantly enough that activists may forgive him. "He could get a second chance."
Republican leaders in two early primary states also see Rubio as a viable candidate.
"My take is that nothing has changed. He's taking a hard look at running despite the news of recent weeks," said Matt Moore, chairman of the Republican Party in South Carolina. Moore caught up with Rubio on Monday as the senator met with Republican leaders and attended fundraisers.
"He's made a lot of friends here. In South Carolina, we've always elected full-spectrum conservatives and he certainly has the ability to speak to social, fiscal and military-inclined conservatives." Adding Rubio's immigrant family history to the mix, Moore said, "He has a potentially unique place in the field."
The head of Iowa's GOP sees a similar path for Rubio, who has visited the state several times and will likely return in February.
"Seeing our spectrum of candidates, I think he would make a wonderful addition," said party chairman Jeff Kaufmann. He recalled Rubio speaking to Republicans there in October. "I'm telling you, he had 800 people eating out of the palm of his hand."
When new Iowa Sen. Joni Ernst, whom Rubio campaigned for, was sworn in this month, the Floridian dropped by her reception and mingled with about 100 Iowans who made the trip to Washington.
On the day Kaufman spoke to the Tampa Bay Times he had received a phone call from Bush, illustrating the hard push Bush has made since declaring on Dec. 23 that he was "actively" exploring a run.
Bush has set a torrid pace, flying around the country to meet with donors and collect money for his new Right to Rise PAC and a Super PAC of the same name that can take unlimited donations.
That's putting a squeeze on other potential candidates but Rubio, hailing from the same state, is at a particular disadvantage because he won't be able to rely on the powerhouse Florida fundraisers that have rallied around Bush.
Still, the junior senator is not backing down.
"I think Jeb Bush is going to be a very credible candidate. I think he's going to raise a lot of money," Rubio told reporters on Wednesday. (Rubio gave a long introduction about what he sees as solutions to the country's problems but the first question he fielded had to do with Bush.)
Rubio's decision-making is complicated because his Senate seat is up for re-election in 2016. He can string things out — he claims he won't — but Florida law will ultimately prohibit him from appearing on the federal ballot twice.
For now he's making all the moves toward a presidential run and says he can mount a credible campaign "which I believe we can do irrespective of who else is in the race."
Miami Herald staff writer Marc Caputo contributed to this report. Contact Alex Leary at email@example.com. Follow @learyreports.