WASHINGTON -- Stuart Stevens, the top strategist for Mitt Romney's presidential campaign, declared to an audience of reporters at a breakfast last month that electing Hillary Rodham Clinton would be like going back in time. "She's been around since the '70s," he said.
And at a conservative conference earlier in the year, Sen. Mitch McConnell of Kentucky, the Republican leader, ridiculed the 2016 Democratic field as "a rerun of 'The Golden Girls,'" referring to Ms. Clinton, who is 65, and Vice President Joe Biden, who is 70.
The 2016 election may be far off, but one theme is becoming clear: Republican strategists and presidential hopefuls, in ways subtle and overt, are eager to focus a spotlight on Ms. Clinton's age. The former secretary of state will be 69 by the next presidential election, a generation removed from most of the possible Republican candidates.
Despite her enduring popularity, a formidable fundraising network and near unanimous support from her party, Ms. Clinton, Republican leaders believe, is vulnerable to appearing a has-been.
"Perhaps in the Democratic primary and certainly in the general election, there's going to be an argument that the time for a change of leadership has come," said Republican strategist Karl Rove. "The idea that we're at the end of her generation and that it's time for another to step forward is certainly going to be compelling."
A yesterday-versus-tomorrow argument against a woman who could be the last major-party presidential nominee from the onset of the baby boom generation would be a historically rich turnabout. It was Ms. Clinton's husband, then a 46-year-old Arkansas governor, who in 1992 put a fellow young Southerner on the Democratic ticket and implicitly cast President George H.W. Bush as a Cold War relic, ill-equipped to address the challenges of a new day. Bill Clinton then did much the same to Bob Dole, a former senator and World War II veteran, in 1996.
A Republican approach that calls attention to Ms. Clinton's age is not without peril, and Democrats predict that it could backfire.
"They would go to that place at their own risk," said Rep. Nancy Pelosi of California, the Democratic minority leader and first female House speaker, noting that "Age is like art -- it's a matter of interpretation."
Ms. Clinton, while silent about a 2016 run, has returned to the speaking circuit and plunged back into the public policy conversation. More to the point, she has sought to effect a with-it sensibility, not only creating a Twitter account but also using a picture of herself in dark sunglasses for an avatar and posting about "taking selfies."
If Ms. Clinton seems to know what awaits her, that may be because Republicans have tipped their hand about how they will frame the 2016 contest.
Alarmed over President Barack Obama's success with younger voters in the last two White House campaigns, Republican officials are bickering over how to appeal to them, with some advocating moderation on social issues like same-sex marriage and others focusing on improving tactics and the use of technology. But there is an emerging consensus that the party stands a better chance by contrasting a younger nominee with Ms. Clinton, a Goldwater girl turned Watergate investigator.
Sen. Marco Rubio, a 42-year-old Florida Republican, drops the names of rappers like Pitbull and Jay-Z. Sen. Rand Paul, a 50-year-old Kentucky Republican, has coined a term for millennials, "the Facebook generation," and is courting young voters with denouncements of the surveillance state.
Besides Jeb Bush, 60, a former Florida governor who is seen in Republican circles as unlikely to run, the Republican field for 2016 largely consists of hopefuls in their 40s and early 50s. Gov. Chris Christie of New Jersey turned 50 last year.
And having witnessed Mr. Obama's dismantling of John McCain and Mr. Romney, they are eager to demonstrate that they represent a new generation.
"The reality is, when you look at the Democrats, they've got old, tired ideas being produced by old, tired candidates," Gov. Bobby Jindal of Louisiana, 42, said in an interview this month, citing "more government and more spending" for the ideas but not referring to any candidates by name.
Of all the would-be candidates, Mr. Paul may be the most heavily engaged in trying to build younger support. He has seized on recent disclosures about surveillance by the National Security Agency and has argued that millennials would favor someone with his security views over the more hawkish former secretary of state.
"If anything, she's even more aggressive on foreign policy and more aggressive on giving power to the security state than the president," he said of Ms. Clinton. And, Mr. Paul added, his mix of libertarianism and federalism resonates with young voters.
"The youth are attracted to people who don't want to lock them up and throw away the key for marijuana," he said. "In some ways, the older Democrats have become more staid and status-quo-like than some of us Republicans."
Any attempt to call attention to an older woman's age could suggest a double standard: Ronald Reagan was 69 when he won the presidency in 1980 and was in his 70s four years later when he won 49 states.
"I would remind my Republican friends that Reagan got 59 percent of the youth vote when I was in college, and he was the oldest guy to ever run for president," said Paul Begala, a Democratic strategist who advised Bill Clinton.
Mr. Reagan was the exception: Every other modern president has been no more than 10 years older than his predecessor.
For her part, Ms. Clinton has dismissed questions about whether her age would preclude a second White House bid, and people who have seen her at recent speeches in Chicago and Grand Rapids, Mich., said she looked refreshed and energized.
"I am -- thankfully, knock on wood -- not only healthy but have incredible stamina and energy," she said in an ABC interview at the end of last year. Her aides declined to comment or make her available for an interview.