Our fascination with polls sometimes produces premature conclusions about next year’s presidential race, including the assumption that Elizabeth Warren and Joe Biden will fight it out for the Democratic nomination. Past polling a year before elections has demonstrated scant predictive value: for 2004, Wesley Clark and Howard Dean were the clear Democratic front-runners, but neither survived the early primaries; John Kerry, who grabbed the nomination, ran fifth at this point.

Four years later, for 2008, Rudy Giuliani was way ahead among Republicans—topping the ultimate nominee, John McCain, more than 2 to 1. And in 2016, Donald Trump was a full six points behind then front-runner Ben Carson—who’s now in Trump’s cabinet. Primary contests are unpredictable, particularly with complicated races and multiple candidates. There’s still time for new entrants like Mike Bloomberg, or some other surprise latecomer, to shake up the faltering Democratic field.