WASHINGTON – In announcing his formal candidacy for the presidency, Florida Sen. Marco Rubio started out in the shadow of a video – Hillary Clinton’s electronic declaration that she is after the same job.

Making his opening bid at a Miami rally, Rubio immediately took aim – not at the host of fellow Republicans harboring the same ambition but at the Democratic frontrunner, who so far has no serious challenger in her own party.

At age 43, Rubio played the generation card. Speaking of the 67-year-old Clinton, he began: “Just yesterday, a leader from yesterday began a campaign for president by promising to take us back to yesterday.” But, he added, “Yesterday is over and we’re never going back.”

In so saying, Rubio seemed to be putting the cart before the horse. First he must beat the competition of a dozen or more fellow Republicans also aiming their fire at arguably the world’s most famous woman, to lead their own party against her in 2016.

One of them is a fellow Floridian, former Gov. Jeb Bush, who at 62 could also be seen as a target of Rubio’s generational barb.

In a National Public Radio interview, Rubio took pains to say he wasn’t running against his “friend” or “anybody in this (Republican) field,” while insisting that “this election is a generational choice about what kind of country we will be.”

In a sense, the Rubio pitch is a throwback to more than half a century ago, and another 43-year-old named John F. Kennedy.

He used his boyish appearance and manner to steamroller his way to the Democratic nomination over old-style party arm-twister Lyndon Johnson, then went on to defeat the awkwardly square Richard Nixon for the presidency itself.

But Kennedy, who by that time had served for 13 years in the U.S. House and Senate and was a decorated World War II veteran in the Pacific, came into office on a wave of personal charm and sophistication, combined with steely resolve. His rallying call for fellow Americans, to “ask not what your country can do for you, ask what you can do for your country,” ignited a fire of patriotism that served him well.

Rubio has served only four years in the Senate and comes off as infinitely more boyish, relying on his story as the son of working-class immigrants amid a national argument over immigration and granting a path to American citizenship for 11 million undocumented foreigners.

Rubio’s early support for a Senate bill endorsing such a path put him in conflict with conservatives in his party.

He has sought to compensate with robust criticism of the proposed resumption diplomatic and economic relations with Cuba, and of efforts to strike a deal with Iran on its development of nuclear power short of creating a nuclear weapon.

In his declaration of candidacy, Rubio also took aim at President Obama, charging his administration with “appeasing our enemies” and “betraying our allies.” He thus remains in step with the other contending Republicans in running against a lame-duck chief executive who will not be on the ballot in 2016.

Still, the advantage of youth seems unlikely to be of much use to Rubio in the effort to build a campaign war chest sufficient to compete with the likes of Bush, who has been aggressively raising money from major donors in and out of Florida.

In that light, it is Jeb Bush, son and brother of former presidents in a well-heeled political family, who seems more akin to the Kennedy of 1960 who could count on a wealthy and ambitious father to bankroll his son.

Joe Kennedy was said to have remarked he was willing to shell out for a victory, but was damned if he would buy a landslide.

So Marco Rubio may be biting off more than he can chew in playing the generational card, absent the money it will take to go the route between now and next year’s voting.

Editor’s note: Jules Witcover’s latest book is “The American Vice Presidency: From Irrelevance to Power,” published by Smithsonian Books. You can respond to this column at juleswitcover@comcast.net.