Independent Vermont senator Bernie Sanders is in the lead for the Democratic nomination according to a new ranking by the Hill. Last week, Hill reporters interviewed Democratic insiders and reported that although no candidate is clearing the field, Sanders, former Vice President Joe Biden, Massachusetts senator Elizabeth Warren and others were generating excitement among top Democrats. The toplines of recent polls seem to agree. Sanders led in New Hampshire as well as multiple national polls (Biden also led in a national poll and was second in the New Hampshire poll).

So is Sanders actually the front-runner?

Maybe, maybe not. Either way, I’m not sure that’s the most important question at this point in the primary process. Democrats are certainly in the early phases of competition for the 2020 nomination, but most voters don’t really tune into the contest until we get much closer to the Iowa caucuses. So rather than trying evaluate whether Sanders is or isn’t the front-runner, I’m going to run through a few of the issues I’m tracking and explain why they might help you watch the Democratic primary in a different way.

Don’t just look at the toplines—compare results to his past performance.

Bernie Sanders won 23 contests and about 43 percent of the popular vote in the 2016 Democratic primary. His support was built partially on a liberal base: He often won very liberal and young voters, but it wasn’t always clear how many of them were specifically casting votes for him rather than against Clinton.

Looking at the current poll numbers gives us one window into that question. Sanders won 31 percent of the vote in the Granite State poll of New Hampshire, but he won 60 percent of the vote there in 2016. Sanders also earned 24 percent of the support in survey by Democratic pollsters Public Policy Polling. He won 43 percent of the overall Democratic primary vote.

The difference between his current and past support could be spun in a couple of different ways. You could argue that most of his 2016 support was soft and that some of his backers could be lured away by another candidate. You could also argue that a showing in the 20 percent to 30 percent range would provide a base he could build on to win the nomination.

The point here isn’t to say that Sanders is or isn’t winning—it’s to show that it’s helpful to add some historical context to topline poll numbers and gain some insights into the broader contours of the Democratic primary electorate.

Watch the composition and size of the field—and remember that we’re probably not polling all the right candidates yet.

It’s also worth noting that we don’t know which candidates will and won’t run yet. As Micah Cohen has noted, about half of the candidates that appear in early surveys typically don’t even run for president. And both the size and composition of the field matter.

I’ve written about the risks of a large Democratic primary field for FiveThirtyEight and RealClearPolitics. I won’t rehash the entire argument here, but essentially Democratic primary rules (candidates are allotted delegates on a proportional basis based on their performance in each state) make it easy for a multicandidate race to end in a situation (e.g. three candidates take 40 percent, 35 percent and 25 percent of the delegates respectively) where either unbound “superdelegates” (more on them later) crown the plurality winner as nominee or candidates are forced to make deals with each other.

If the Democratic primary field contains more than two viable candidates, the possibility of this sort of outcome increases. So it’s worth watching how big the field gets.

The ideological composition of the field matters, too. One of Donald Trump’s key advantages in the 2016 Republican primary was a solid base of downscale, cultural conservatives. Starting with that base, he was able to build a coalition that could win in a multicandidate primary. Many of Trump’s competitors couldn’t do this—they had to compete to build a base, and eventually were forced out of the race.

So as Democratic candidates move closer to or further from a White House run, it’s worth asking what the composition of the field might look like and how that could change the final results.

In other words, the size and the shape of the field matter. So don’t just watch the polls—watch which candidates are moving toward a run, which aren’t and think on which demographic and ideological lanes might end up crowded or vacant.

Watch for changes in the rules.

This might seem like the least sexy item in an already unsexy list. But rules shape the results of elections in powerful ways (see the previous section on proportional rules), so it’s important to understand when they might be changing.

Most notably, it looks like Democrats may decrease the number of unbound delegates (also called “superdelegates”) for the 2020 cycle. These delegates (many of whom are elected officials or party leaders) usually comprise roughly 15 percent to 20 percent of the delegates to the convention.

Decreasing the number of superdelegates represents a tradeoff—the Democratic primary process would become more “small-d democratic” while becoming less stable. Superdelegates do dilute the power of the rank-and-file voter (voters don’t control who the superdelegate votes for), but they also function as a sort of airbag for Democrats. If their convention is headed for turmoil (e.g. if no candidate won a clear majority of pledged delegates) the Superdelegates can collectively swoop in and solve the problem.

It’s not my place to say whether Democrats should decrease the superdelegates’ power – but it’s worth watching these tradeoffs and trying to track how decisions that are happening now will shape the course of a primary two years down the road.