Hillary Rodham Clinton hasn’t made clear yet whether she will run for the Democratic presidential nomination in 2016. If she does, she will be the front-runner. (Bebeto Matthews/AP)

Conventional wisdom — and even some unconventional wisdom — dictates that Hillary Rodham Clinton is running for president in 2016.

A universe of super PACs and other organizations has been built, and staffed by former Clinton operatives, to prepare the way for Hillary. And yet, running through all of these preparations is a current of uncertainty about whether the former first lady, senator and top diplomat will, you know, actually run.

The thinking is that Clinton would never let such extensive efforts go forward if she, in her heart of hearts, wasn’t planning to enter the race. But that, like most of what we think we know about Clinton and her plans, is based not on facts but on interpretation.

One thing that everyone — those who want Clinton to run and those who don’t — agrees on is that she has simply not made up her mind yet and probably won’t for some time. So, what happens if she decides not to campaign for the White House? In a word: chaos. Here’s why:

1. There’s a panoply of ambitious Democrats who watched Barack Obama leapfrog them in 2008 and won’t want to miss their opportunity this time.

2. If Clinton announced on March 1, 2015, there would be only 10 months before the calendar turned to 2016. Given how much her candidacy — or at least her decision-making about her candidacy — has and will continue to freeze the field, there would be a mad scramble for donors, activists and key consultants in early states, the likes of which we haven’t seen in modern presidential history.

3. There is no obvious front-runner in a Clinton-less field. Vice President Biden would be the nominal favorite for the nomination, but you could also make a credible case for New York Gov. Andrew M. Cuomo, Sen. Elizabeth Warren (Mass.) or even Sen. Kirsten Gillibrand (N.Y.) to occupy that space.

To be clear, we still expect Clinton to run. But if she doesn’t, the race for the Democratic nomination in 2016 could be one for the ages. Here, we rank the 10 candidates considered to have some possibility of running for or winning the Democratic nomination in two years. We’ve split them into four tiers; they are listed alphabetically within each tier.

First tier (The Clinton wing)

Hillary Rodham Clinton: She is the biggest front-runner the Democratic Party has ever seen. If she runs, she (almost certainly) wins.

Second tier (If she says no, then . . .)

Joe Biden: The vice president wants to run. But he knows he would start way, way, way behind Clinton and might not be able to make the race close. On the other hand, if Clinton passes, Biden is in — if not the next day, sometime shortly thereafter.

Martin O’Malley: The Maryland governor makes the second tier because he is the most credible candidate most likely to run, even if the 2016 field includes Clinton. Why? Because O’Malley is term-limited out of office at the end of the year, with no obvious next step other than running for president.

Brian Schweitzer: The former Montana governor wants to run for the White House. While he (sort of) demurs publicly, his statements all have a sort of wink-wink, nudge-nudge, you-know-what-I-am-saying-ness to them. Although most Democrats in Washington roll their eyes at the idea of a Schweitzer bid, he is a gifted and charismatic communicator.

Third tier (Not interested, but . . . )

Andrew Cuomo: The New York governor’s professed lack of interest in the race, once regarded as a sort of coyness that he would eventually shrug off, is now seen as a sign that he doesn’t really want to run. We continue to believe that a race without Clinton would be too hard for the ambitious Cuomo to resist, however.

Kirsten Gillibrand: The senator from New York has emerged as a rising star in the party — a reputation built on her fundraising prowess and her legislative efforts on the issue of sexual assault in the military.

Deval Patrick: After saying for years that he wasn’t interested in running for president, the Massachusetts governor opened the door to the possibility last month. “That’s a decision I have to make along with my wife of 30 years, and she’s a tough one to convince,” Patrick told Politico in a classic open-the-door-a-crack statement.

Elizabeth Warren: Of all nine potential candidates on this list who aren’t Clinton, the senator from Massachusetts would have the most viable path to beating the former secretary of state. A hero among liberals, who don’t love Clinton and never will, Warren is the sort of anti-corporate, anti-Wall Street populist that many Democrats thought they were getting with Obama.

Fourth tier (Just. Not. Happening.)

Cory Booker: The Newark-mayor-turned-senator has a bright political future. But he remains relatively raw, politically speaking, and is plenty young enough to wait a few elections before making his (inevitable) presidential run.

Bernie Sanders: In an interview with the Nation this month, the self-avowed socialist senator made clear that he is dead serious about a campaign. “I am prepared to run for president of the United States,” Sanders said. His candidacy would be fascinating, if ultimately doomed to the margins of the race.