In a terrific piece assessing Hillary Clinton's time as secretary of state, Politico's Susan Glasser highlights what we believe could well Clinton's Achilles heel in 2016: Caution.

Glasser writes:

I asked an array of smart foreign policy thinkers in both parties to weigh in, and they pretty much all agreed that Clinton was both more cautious and more constrained than [Secretary of State John] Kerry. Their argument is over whether and to what extent that was a consequence of Clinton herself, the limits placed on her by a suspicious and eager-to-make-its-mark first-term White House, or simply it being a very different moment in world politics.

Later in the piece, Glasser quotes Bush administration State Department official David Gordon saying that it's "hard to avoid the conclusion that for Clinton, the SecState role was substantially about positioning her to run for president, especially in terms of looking ‘tough’ on some of the big issues: Iran sanctions, reassuring Asian allies."

One of the defining traits of Clinton as a politician -- in the 13 or so years we have to study -- is that she tends to be decidedly risk-averse. Caution is the watchword. When she came to the Senate, she did everything she could to blend in -- assiduously avoiding using her star power to draw attention to herself or her pet issues. When she ran for president in 2008, she did so as, essentially, the incumbent -- taking very few gambles (calculated or otherwise) when it came to how she was positioned in the race or the policy positions she adopted.

Take, for example, Iraq. Clinton voted for the use-of-force resolution against the country in the early 2000s -- a vote widely regarded by "smart" Democratic strategists as the safe vote for Democrats who wanted to run for president down the line. (John F. Kerry, the party's nominee in 2004, also voted for it. Side note: Clinton's caution is evident in her decision to pass on a run for president in 2004.) As the 2008 campaign began, Clinton stuck by that vote -- refusing to take the risk that, for example, John Edwards took by apologizing for voting in favor of the use-of-force resolution.

Both the vote and her refusal to back away from it gave Barack Obama a justification for his candidacy and a foothold to cast himself as the anti-Clinton.

Even in her post-State department career, Clinton -- and her people -- have been reluctant to weigh in on matters of foreign or domestic policy.

Some of this is understandable. Clinton is one of the most watched people in the world, and any time she says anything it will be searched for hidden meanings about (a) her 2016 plans and (b) her real feelings about President Obama. No other politician with the exception of Obama is so closely watched.

And, as Glasser notes in her piece, Clinton's caution as secretary of state is also partly attributable to the way in which she was viewed by Obama (and his senior aides) and the challenges presented to her (or, more accurately, not presented to her) in her four-year term.

Still, it's not just as secretary of state where Clinton has exhibited a caution (bordering on paranoia) that has hurt her politically. Why didn't Clinton more directly tout her potentially history-making status as the first female president in 2008? Because conventional wisdom -- at least in her campaign -- was that emphasizing that part of her candidacy was an unnecessary risk. And we all know how that turned out.

Clinton's caution may wind up never hurting her. With Massachusetts Sen. Elizabeth Warren all-but-definitively eliminating herself as a 2016 candidate, it's hard to see an Obama-like challenge from Clinton's more risk-ready left flank. Still, it would surprise us if someone -- Russ Feingold? Howard Dean? -- didn't run as the shake-it-up candidate.  Safety in politics is rarely a virtue.