This article originally appeared on Slate.

Vice President Joe Biden spoke in Iowa on Thursday saying exactly what you'd expect him to say about the success of the Obama administration and how it should be carried on: "Those seeking to lead the nation should protect and defend and run, yes run, on what we've done; own what we have done. Stand for what we have done, acknowledge what we have done, and be judged on what we have done. ... Some say that would amount to a third term of the president. I call it sticking with what works and what we oughta do."

A third Obama term. The vice president isn't the only one who feels this way. This, of course, is what Republicans have been saying Hillary Clinton's presidency would be for months. Biden didn't introduce this idea, but it's one thing for Republicans to say it, it's another thing for the vice president to bolt it onto the eventual Democratic nominee.

When I heard it, I was fresh from having read David Axelrod's book Believer about his life in politics from his first political rally at age 5 to the celebration of Obama's re-election in Chicago on election night in 2012. In the book, he recounts the details of the 2008 campaign, when Obama repeatedly said he didn't want to give "John McCain the chance to serve out George Bush's third term."

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This is a standard attack. Indeed, Democrats are raising money today playing on the idea that Jeb Bush is a third George W. Bush term. The big obvious difference in 2016 is that Obama is much more popular right now than George Bush was at the end of his presidency. Bush's approval rating was 28 percent in the 2008 election night exit poll. Right now Barack Obama's approval rating is 47 percent in the Gallup poll, almost 20 points higher. If the economy continues to improve, that number could climb higher still and you could imagine Hillary Clinton saying, If by third term you mean another 59 months of continuous job growth and falling unemployment, then yes I'll be a third term.

But what Axelrod's book highlights is the way in which this kind of attack presents challenges that go well beyond mere association. In the 2008 campaign, the Bush's "third term" charge was a way to highlight the contrast between the old and the new. McCain was a part of the Washington system, Obama was from outside that system. The attack created an appetite for the new, the flavor that Obama happened to be selling. Hillary Clinton may be a strong candidate, but she will never be able to pull off new.

Axelrod writes about a crucial lesson he learned from working on so many mayoral races. Voters want a "remedy, not [a] replica" in the next candidate, even when the incumbent leaving office is well-liked. He says this rule--which he learned most directly in the 1989 race for the mayor of Cleveland where Michael White, the Democrat, followed the popular incumbent Republican George Voinovich--applies to presidential campaigns, too. He wrote to Sen. Obama in 2008: "When incumbents step down, voters rarely opt for a replica of what they have, even when that outgoing leader is popular. They almost always choose change over the status quo." This is a different formulation of what President Obama was talking about recently when he said voters wanted "that new car smell." Clinton is associated with the status quo even more because she has the Obama years and the Clinton years attached to her.

Given this view, simple distinctions between Obama and Clinton on policy or positioning won't be enough to break the third-term lock. It will be very hard for Clinton to offer herself as a remedy because there is nothing that makes her so constitutionally different from Obama that voters will notice. She is probably, for example, a better deal-maker and would work harder at connecting with Republicans, but that's hardly a vast distinction that makes voter sit up. Gender is an obvious distinction, but that's not the basis for a presidential platform.

Perhaps this is one of the reasons Clinton is working so hard to come up with a message that is so unique and powerful it looks new. Amy Chozick of the New York Times reports that Clinton has consulted more than 200 experts in her effort to craft an economic message. She's not just trying to come up with a policy that creates distance, but one that achieves escape velocity.

Were Clinton actually campaigning right now, she'd probably have had to spend the day answering questions about where she stands relative to President Obama. Is she a third term or not? Perhaps she would ace that test, but this charge is also a trap to make Clinton bungle into the most damaging caricature of her--that she is excessively political. If the public doesn't think there's any big difference between what she's offering and what President Obama would offer in a third term, Clinton's efforts will look like Third Term Monte, a sleight of hand confidence game.