There is nothing particularly flashy about the endorsements that have been rolling in for Sen. Marco Rubio lately: a handful of Republican members of Congress, mostly junior and not terribly influential.

But upon closer inspection, there is something they share. Like Rubio, almost all are young. They include Mia Love of Utah, 39, a freshman representative and the only black Republican woman in Congress; Jaime Herrera Beutler of Washington, who was first elected to the House five years ago when she was only 31; and Cory Gardner of Colorado, who at 41 is the second-youngest member of the Senate.

Age, or the conspicuous lack of it, is something that infuses almost every element of the Rubio campaign — from the punch lines he delivers on the stump (“I’m 44, but I feel 45,” one well-worn joke goes), to the under-40 workers who make up the vast majority of his staff, to the shots he takes at his opponents, like “Yesterday’s over,” that are supposed to make them seem old.

By running a campaign that emphasizes his youth and appeal as a figure of generational change, Rubio, in essence, is trying to reverse the roles that Democrats and Republicans have played in presidential elections for the last generation. And he is trying to scramble the identity politics that have taken shape within both parties, particularly after a 47-year-old Barack Obama excited young voters in 2008 with his own message that it was time for dramatic change in Washington.

In their efforts to disparage Hillary Rodham Clinton, for example, Rubio campaign researchers have combed over hours of footage searching for clips that make her sound like a relic. One discovery: Clinton in New Hampshire recently compared taking questions from the audience to “The Gong Show,” a game show popular in the 1970s. The campaign turned another clip of Clinton saying, “I come from the ’60s — a long time ago,” into an online ad that ends with Rubio saying, “If I am our nominee, we will be the party of the future.”

It is a difficult line to walk, especially for a politician who is being attacked as precocious, impatient and too busy furthering his presidential ambitions to show up to work in Washington.

Rubio’s challenge is made more daunting by the fact that he is trying to win the nomination of a party that has grown older, whiter and more conservative. Seeking to become the first Hispanic president, he is the youngest person in the Republican field this year.

The opposite situation is playing out in the Democratic Party. Clinton, who if elected will be 69 by the time she occupies the Oval Office (only Ronald Reagan was older), is relying on a coalition of voters that is more black, Hispanic, liberal and young.

“It’s kind of odd that they themselves are part of a demographic that’s not their natural political base,” said William H. Frey, a professor at the University of Michigan and an expert on demographics and politics for the Brookings Institution. Frey calls this phenomenon “the emerging cultural generational gap,” and notes that unlike in 2008 and 2012, when Mitt Romney, John McCain and Obama reflected their parties’ bases, 2016 could be just the opposite.

Most of Rubio’s Republican competitors are decades older: Donald Trump is 69, Ben Carson 64 and Jeb Bush 62. The exception is Ted Cruz, who is just five months older than Rubio. But almost no one ever mentions Cruz’s youth.

Rubio, who can recite rap songs from memory and recreated a scene from the 1993 film “Sleepless in Seattle” when he proposed to his wife, would be the only modern president whose experience was not rooted in the baby boomer generation.

While Rubio regularly jokes that he feels a haggard 45, his boyish appearance is often one of the first things people mention about him. Bobbie Whitcomb, 72, of Kingston New Hampshire, who heard him speak at a recent appearance, said, “I look at Marco and he’s younger than two of my kids.”

And while he also likes to say he will end up feeling 55 when he is finished with his presidential campaign, he is asking voters to make him the third-youngest president ever, behind only Theodore Roosevelt (42) and John F. Kennedy (43).

He is seeking to lead a country that looks very different from just a few years ago.

Millennials, or those born between 1982 and 2000, now outnumber baby boomers. But though the youngest millennials will not vote for president until 2020 and registering them remains a challenge, the problems Republicans have in winning them over remain immense.

And while Clinton may not enjoy Obama’s standing with younger voters, she has an edge. According to a recent Wall Street Journal/NBC News poll, she would beat Rubio in a general election by five percentage points among voters ages 18 to 34.

Being young is one thing. Being the candidate whose ideas seem fresh and appeal to younger voters is another. And that is where Republicans have fallen short in recent elections.

“The Republicans always misunderstand the Democratic coalition, especially the Obama coalition, as merely identity politics,” said Paul Begala, a former strategist for President Bill Clinton. He argues that Republicans would be making a mistake to think that voters will look at Rubio and give him the benefit of the doubt just because he is a fresh face.

The issue of experience is one of the more complicated ones Rubio will have to overcome.

He and his campaign are working to present him as a steady and tested leader without drawing too much attention to the fact that he has been a politician since he was 26 — a part of his biography that could be poisonous in a Republican contest dominated by candidates who flaunt how little political experience they have.

At times, this has meant rewriting his campaign script. A common question he gets is how he would fare any better in the White House than Obama, another first-term senator who spent just a few short years in national office. (Jeb Bush, a former Florida governor who helped a young Rubio when he was coming up in state politics, often makes a version of this argument against the senator.)

At first, Rubio would answer by pointing to his lengthy résumé as both a state legislator and speaker of the Florida House.

He has since dropped the references to his résumé, and now dismisses the idea that leadership ability is tied to time in office.

“It’s clear that the issue with him is not that he didn’t have executive experience,” Rubio told CBS News about Obama this month, offering a variation of his pat answer. “It’s that his ideas do not work.”

But history has shown that Republican primary voters tend to pick experience over youth in their presidential candidates, someone broken in and battle tested instead of green and idealistic.

That has meant nominees like Reagan (a former governor of California who was just a few days shy of his 70th birthday when sworn in), the first George Bush (a former congressman, director of the CIA and vice president), Bob Dole and McCain (both veteran senators and war heroes.)

And with this in mind, Jeb Bush’s campaign has rolled out its own endorsements. Two of the highest-profile ones so far have come from the former senator Alan Simpson, 84, and Dole, 92.