Republican presidential candidate Donald Trump greets supporters after his rally at Ladd-Peebles Stadium in August in Mobile, Ala. (Photo by Mark Wallheiser/Getty Images)

Several months ago, the New York Times’ David Leonhardt suggested that the geeks had beaten the pundits when it comes to campaign analysis, saying that “data-wielding political analysts have trounced the pundits who judge campaign based on crowd size and vague notions of momentum.”

I was skeptical, and the subsequent months have born out the skepticism in one sense: Commentators are still judging campaigns based on the size of the crowds — and especially the crowds who want to see Donald Trump and Bernie Sanders. I think that’s not really a controversial claim, but here are some links if you need them.

The big question, obviously, is whether success at attracting big crowds actually predicts success in primaries and caucuses. One argument goes something like: “Wow, if people are willing to stand in line out in the cold for hours to see the candidate speak, then surely they are willing to spend the time and effort to show up and vote.”

That may seem plausible on its face, but I’m going to inject a note of caution. It goes like this: If you want to see Trump or Sanders speak, you have to go to the rally. But if you want to see Trump or Sanders win, you do not have to vote.

Here’s what I mean. The benefits you might get from a rally — a chance to express your passion for a candidate, be inspired or entertained by their speech, enjoy the company of other supporters — depend on going to the rally. If you don’t go, at best you’ll hear a few soundbites from the speech on the news. You won’t feel the excitement. You won’t get to see the show, as it were. You’ll lose out.

But voting is entirely different. Perhaps the key benefit you’ll get from an election — seeing your preferred candidate win — doesn’t really depend on whether you vote. Obviously your one vote is very unlikely to determine the outcome of the election. You won’t necessarily lose anything if you stay home on Election Day. You could stay at home and still be cheering after the returns come in.

In other words, the free rider problem looms large when it comes to voting, but much less so when it comes to attending a rally.

Of course, at least some people who attend the big rallies for Sanders or Trump are dedicated, passionate supporters who will vote. And clearly the candidates are working to mobilize supporters for the various caucuses and primaries.

I’m simply pointing out that you can’t analogize the two activities — attending a rally and voting — as easily as people sometimes do.