A funny thing happened this week on the long and winding path to 2016: The unstoppable Hillary Clinton machine may have revealed -- or reminded us -- of its Achilles heel: Caution bordering on total risk-aversion.

Clinton, as not only a former Secretary of State but also the widely regarded frontrunner to be the 2016 Democratic nominee is she runs, came under considerable pressure to say something about President Obama's push for Congressional approval of a military strike on Syria. (That pressure increased after Clinton took to Twitter to congratulate Diana Nyad on her swim from Cuba to the Florida Keys over the weekend.)

The Clinton operation responded on Wednesday with a statement to Politico and the Washington Post among others expressing her support for the "President’s effort to enlist the Congress in pursuing a strong and targeted response to the Assad regime’s horrific use of chemical weapons."

That statement didn't come from Clinton herself, however. Nor did it come from a top aide speaking on the record. Instead, the Clinton team insisted the quote be attributed only to a "Clinton aide".

There's no doubt Clinton-world has its reasons for this anonymity. As a former Secretary of State, Clinton is clearly conscious of not getting in the way of her replacement or getting crosswise with the president. And, because she is who she is, anything Clinton said would be (and will be) immediately parsed to death in search of hidden meaning or read as a subtle attempt to distance herself from the Administration's policy.

Still, for many political observers, that obsession with caution that borders on paranoia is not new to Clinton world. Her 2008 campaign was in many ways defined by that trait, an unwillingness to take even the slightest of risks -- whether on message or policy -- for fear of what impact it might have. In fact, Clinton's 2002 vote for the use of force in Iraq -- the single vote that likely cost her the 2008 nomination -- was born of a similar penchant to always make the safe rather than the bold move.

That trait may wind up not hurting Clinton in 2016. If she runs, there is a widespread belief that the vast majority of other serious contenders won't. But, it does suggest that if someone (or someones) do decide to challenge Clinton, their best chance would be to go as bold as possible on message and policy grounds in hopes of casting her as a forever defender of the status quo.

Below are our rankings of the ten men and women considered most likely to wind up as the 2016 Democratic nominee. Because there is Clinton and then there is everyone else when it comes the field, we have split the potential candidates into tiers rather than ranking them from one to nine.  The candidates are listed alphabetically by last name within the tiers.

To the Line!

Tier One (The de facto nominee)

* Hillary Clinton: To call Clinton a frontrunner at this point is to undersell the strength of her positioning in the contest.  She is, without question, the candidate best able to finance a national campaign and build the wide variety of early state organizations she would need. She also has a resume that no one else in potential field -- with the possible exception of Joe Biden -- can come close to matching.

Tier Two (If not Hillary, then....)

* Joe Biden: The Vice President's trip to Iowa later this month -- Steak Fry! -- is designed to remind people that he remains actively interested in running in 2016. We've written before that Biden is underrated in a Clinton-less field and we still believe that. He's spent decades meeting and greeting activists (and donors) all across the country and will likely be able to tap into the goodwill for Obama in the Democratic base should he run.  As to the question of whether Biden would run if Hillary did, we don't think he would.

* Andrew Cuomo: Aside from Clinton and Biden, the New York governor is the only person in the field who can plausibly make the case that he has the resume and fundraising chops to win the nomination today. Cuomo started his term with a string of legislative successes that will endear him to liberals nationally -- legalizing gay marriage, stricter gun control -- and doesn't appear to have any real Republican opposition in 2014, meaning he can begin to turn an eye (or both eyes) to a potential national bid.

Tier Three (There's a case to be made but it's not a strong case yet)

* Kirsten Gillibrand: Gillibrand has the fundraising capacity -- she collected $30 million combined in her 2010 and 2012 races -- to eventually make the leap to the second tier. She's also put herself front and center on issues -- sexual assault in the military being one -- that have raised her profile nationally. If Clinton is in, Gillibrand is out. If Clinton passes, however, Gillibrand has a case to make.

* Martin O'Malley: The Maryland governor is the candidate on this list who is most clearly running for president. To his credit, O'Malley has put together a solid team of campaign operatives and consultants and built a record every liberal can (and will) love during his second term as governor in the Old Line State. The question for O'Malley is whether the appeal he quite clearly has on paper can translate into an actual race.

* Elizabeth Warren: No candidate on the list has more potential -- "upside" to borrow an overused NBA draft -- than the freshman Democratic Senator from Massachusetts. She has, to date, expressed zero interest in running (and her political advisers insist she is sincere in that lack of interest) but even so she makes it into our third tier because if she did decide to jump in, Warren would immediately become a contender. Warren is already a rock star among the liberal base and she raised $42 million (not a typo) for her 2012 Senate campaign.

Tier Four (Probably not going to win but could run)

* Cory Booker: The soon-to-be New Jersey Senator could be the highest profile African-American in statewide elected office as attention turns to 2016.  That could be a very powerful position.  But, the whole T-Bone episode doesn't sit all that well with us; Booker could NOT get away with stuff like that under the national microscope of a presidential race.

* Howard Dean: Did someone say a "bold" candidate might be in order to challenge Clinton? Enter the former Vermont governor and 2004 presidential candidate. At an appearance in Iowa (SIREN!), Dean told the Des Moines Register that "at this point, I’m supporting Hillary Clinton." Um...

* Amy Klobuchar: Of the Tier Four folks, the Minnesota Senator is the least well known but could well be the one who moves up the ranks before all is said and done. She's a savvy campaigner who happens to be from the Midwest and, not for nothing, popped into Iowa late last month. Klobuchar's biggest hurdle would be pushing her way into a field crowded with boldfaced names -- even if Clinton doesn't run.

* Brian Schweitzer: There's little question that the former Montana governor thinks he should be president. Just ask him.  There are bigger questions about whether his free-wheeling style and somewhat conservative record as the chief executive of the Last Best Place would sit well with Democratic primary voters.