The Medicare-Eligible Primary
PHOTO: Vice President Joe Biden speaks about proposals to reduce gun violence, Jan. 16, 2013, in the South Court Auditorium at the White House in Washington. U. S. Secretary of State Hillary Rodham Clinton speaks during a news conference at the annual Aus

Barack Obama was a 40-something fresh face when he won the presidency in 2008.  He's gotten older in four years, but he was up against another older man -- Mitt Romney -- to keep his job.

But Hillary Clinton and Joe Biden -- two of the top potential Democratic replacements for Barack Obama four years from now -- will be either in or approaching their 70s when the next presidential election rolls around.

Related: A new ABC News/Washington Post Poll finds Clinton with a 19 percent favorability advantage over Biden.

Smiling, jolly Biden sure did look like he could mount a campaign in a little under four years as he bounded along the inaugural parade route, hale and lively.

In an interview that aired on CNN today, Biden said he hasn't determined whether he'll seek the presidency in 2016.

"Oh there's a whole lot of reasons why I wouldn't run. I haven't made that decision and I don't have to make that decision for a while," Biden told CNN's Gloria Borger.

Asked if he's ready to run against Clinton in 2016, Biden said, "I haven't made that judgment and Hillary hasn't made that judgment."

"In a couple years, I think he's going to take a hard look at it," Beau Biden, the vice president's son and the attorney general of Delaware, said on MSNBC. "I hope he does."

Clinton, in her final days as secretary of state, says she needs a rest from public service and politics. But there isn't anybody who doesn't see her as one of Democrats' top contenders to replace Obama in 2016. She'd be the first woman president, but she'd also be one of the oldest.

She's the most traveled secretary of state in history and newly eligible for Medicare -- she turned 65 on Oct. 26. But Clinton, before a fall and treatment for a blood clot, could clearly still keep up with her younger staffers on whirlwind round-the-globe tours.

She'd be the same age as Ronald Reagan when he took office as the oldest first-termer in history. Biden, at 70 right now, would be the oldest newly elected president to take the oath of office at 74.

Nancy Pelosi bristled -- and maybe rightfully so -- when a 20-something reporter asked recently if she should step down as leader of House Democrats to make room for a younger generation.

"Let's for a moment honor it as a legitimate question," Pelosi said, chuckling. "Although it's quite offensive, although you don't realize it, I guess."

She said the question would never be asked for a man. But it is true that the top three Democrats in the House are all in their 70s.  John Boehner, the top Republican in the country as speaker of the house, is 63. His two deputies are in their 40s.

Anecdotally, age could be a problem. Obama, after all, beat two older men. Bill Clinton beat three older men in presidential races if you count Ross Perot. But usually age is not the overriding issue in a campaign. Reagan actually scored points declaring at a debate with the younger Walter Mondale, "I am not going to exploit for political purposes my opponent's youth and inexperience."

We emailed the Yahoo! News columnist Jeff Greenfield, who has covered a lot of presidential campaigns, to weigh in.

"Despite my having taken a vow of silence on '16 -- it is way way way way way too earlier for this stuff -- here's a general take," he wrote in an email. "Candidates like to define elections as the past versus the future, and they are the future.  But I always thought Ronald Reagan's age was a HELP, because it linked him to a BETTER past -- no one was happy about the present in 1980 -- and Reagan's buoyancy and optimism also made him a 'future' guy." … The question for '16 could be: if folks are happy with how things are, Clinton or Biden may have a good 'experience' argument. If folks are unhappy, their age(s) underscore the 'past' problem. "

Republicans have their demographic issues -- just look at the results from the November 2012 election -- but finding young talent isn't one of them. Their vice presidential candidate was the first politician on a national ticket born after the moon landing. They've got two very young and dynamic Hispanic senators. Democrats only have one. Republicans have two young Hispanic governors. Democrats don't have any.

Obama's Democratic coalition relied heavily on turning out minority voters. The historic nature of becoming the first black president and squaring off against two much older white men can't have hurt his ability to excite minorities.

But what if the choice for voters is Marco Rubio or Joe Biden? Would that change turnout?

The overriding narrative coming out of the 2012 election was that Republicans had turned their backs on Latinos by supporting conservative immigration policies. But -- and we're heading into hypothetical land here -- if Marco Rubio can help engineer some sort of immigration compromise, that narrative could change very quickly. He might have a more difficult time in some Republican primaries, but he would be a much stronger general election candidate.

None of this is to say that Democrats don't have exciting new blood in their stream that includes many women and minorities and younger politicians, some of whom will certainly eye a run in 2016. But there is no doubt they have a more established establishment.

Age is not a cause of concern for many Democrats quite yet.

"I don't think Democrats are suffering from a lack of next-generation leaders," said Simon Rosenberg, who is President of the NDN, a left-leaning think tank in Washington. "They just have a lot of good older leaders, too."

Rosenberg pointed to politicians like Andrew Cuomo, the New York governor; Cory Booker, the Newark, N.J., mayor; and Gavin Newsom, the California lieutenant governor, as part of the younger generation of Democrats.

And he said there are problems for a lot of younger politicians, too.

"They could be young, but they also have to be good," he said, arguing that Paul Ryan didn't draw any young people to the Romney ticket. And he argued that Democrats' party position on health care, immigration reform and financial issues will help them keep Latino votes.

It will ultimately be policy positions that solidify the coalition of voters that twice elected Obama, he said.

"The Obama coalition that has been built, to me, is a durable coalition that will be able to be transferred to the next nominee," he said, "as long as they know what they're doing."

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