U.S. Secretary of State Hillary Clinton (L) greets Sen. Elizabeth Warren (D-MA) as they arrive for Sen. John Kerry's (D-MA) confirmation hearing before the Senate Foreign Relations Committee to become the next Secretary of State in the Hart Senate Office Building on Capitol Hill January 24, 2013 in Washington, DC. (Photo by Chip Somodevilla/Getty Images)

Hillary Clinton, after much debate within her inner circle, appears to have put off formally entering the 2016 presidential race until the spring of 2015.   "Hillary Rodham Clinton is considering the nitty-gritty details of how and when to organize a presidential campaign amid signs that she will postpone making her shadow campaign official until later in 2015 than expected, according to advisers and Democratic strategists," wrote WaPo's Anne Gearan and Matea Gold this week. That jibes with plenty of other reporting on the matter and seems as close to a consensus opinion as you will get when it comes to the remarkably opaque decision-making process of the former Secretary of State.

While there are plenty of reasons that argue in favor of waiting -- legal ones in terms of how she incorporates (or doesn't) the various outside groups that have blossomed in support of her over the past few years, political ones about looking less, well, political for as long as possible -- there's also a big reason why she should at least consider announcing sooner rather than later. And it's named Elizabeth Warren. Or, at least, the energy and passion among liberals that is, at the moment, channeled through Warren.  An attempt to draft the Massachusetts Senator launched formally this week and her stern opposition to the CRomnibus bill because of a provision that would ease derivative trading by corporations drew scads of national coverage.

That's not to say Warren is running or even thinking about it at the moment. But, let's say the next three months play out like the last three months. The dominant narrative remains that Clinton is the heavy favorite to be the Democratic nominee. But that storyline is accompanied by another one -- which is that the heart of the Democratic party really wants Warren.  And, as that storyline continues, more and more people hear about it; an actual movement develops, all fueled by the anti Wall Street populism that Warren embodies.

If Clinton waits until April, let's say, to announce, it's uniquely possible that the populist/draft Warren movement in the party has grown strong enough that it has forced the Massachusetts Senator to reconsider her past denials of interest in the race. And, if Warren runs, it's a totally different race for Clinton than if she doesn't. (To be clear, Clinton would be a favorite over Warren. But not a huge one.)

So, why not get in earlier -- before the Warren movement gets any more energy or excitement behind it? Plus, the sooner she gets in, the sooner Clinton can start raising the money and building the campaign infrastructures that should be her biggest advantage in the race. And, what if she used her formal campaign announcement to deliver a message on income inequality -- sending a message about how central that would be to her candidacy in 2016?

In short: Make it as hard as humanly possible for Warren to reconsider or for the movement trying to get her to reconsider to gain steam. Be the prime mover. Act and make Warren, and everyone else, react.

Below are our rankings of the six people either running, talking about running or being talked about as potential runners for 2016 for the Democratic nomination. The candidate ranked number one -- let's not pretend here: it's Clinton -- is considered the most likely nominee.

6. Vermont Sen. Bernie Sanders: Sanders is not a Democrat -- he;s a Socialist -- and he's not going to win the Democratic nomination for president. Yet, he still appears on this list, because there's a decent chance he will run. And that's more than we can say for a lot of folks. For now, Sanders is the most likely outlet for liberals who think Clinton is too closely allied with Wall Street. But, the idea that a guy who calls himself a "socialist" is going to gain real traction in this race is hard to believe.

5. Former Virginia senator Jim Webb: The one-term senator is the first real entrant in the 2016 presidential race. And there won't be any more surprising candidate. That's because Webb retired from the Senate after one term and never seemed to enjoy the political process very much -- especially the campaigning part. The fact that this is the guy some are holding up as a more liberal alternative to Clinton just doesn't really make sense. But he is a former senator and Navy secretary, so he's got some national profile.

4. Maryland Gov. Martin O’Malley: A few years ago, O'Malley would have been seen as Clinton's biggest obstacle. He's a capable politician, a two-term governor and has national experience as Democratic Governors Association chairman. But O'Malley's two terms as governor ended on a low note. His approval rating dropped to 41 percent (in a blue state), and his lieutenant governor lost in the most shocking upset of the 2014 election. O'Malley seems one of the most likely big-name politicians to run, but he's hardly looking strong these days.

3. Vice President Biden: He's a two-term Vice President of the United States, a longtime senator, and he wants to run for president. Yet almost nobody thinks Biden can give Clinton a run for her money. The reason? He's a little too "Uncle Joe" and not really "President Biden." We keep going back to it, but we think it's illustrative: A Quinnipiac University poll last year showed 65 percent of Americans didn't think Biden would make a good president. And only a bare majority of Democrats (51 percent) said that he would. Biden needs to show a more presidential side before he has a shot.

2. Massachusetts Sen. Elizabeth Warren: Warren is the the beating heart of the Democratic base. She is also the only person on the list other than Clinton with a track record of raising lots (and lots) of money. (Warren raised $42 million in her 2012 victory over then Sen. Scott Brown.) Combine those two factors and you see why the possibility -- albeit it slim -- chance of a Warren presidential bid intrigues so many people.  She still is giving no indication she wants to run. But, if ever that changes, Warren is a bad matchup for Clinton and could give the former Secretary of State real problems.

1. Hillary Clinton: The Warren buzz has to make some longtime Hillary allies a little skittish, reminding them of another liberal firebrand senator six years ago. Given that experience, however, Clinton (and her people) should be more ready in the unlikely event Warren does reverse course and run. Clinton, over the past year, has begun to talk much more about income inequality -- a clear rhetorical bow in Warren's direction and a subtle attempt to co-opt the energy forming behind the Massachusetts Senator.  Assuming Warren stays out, Clinton starts the primary further ahead than any non-incumbent in modern history.