Washington (CNN) Over the weekend, Elizabeth Warren spoke in front of 15,000 people at a campaign rally in Seattle, Washington.

It was, by her campaign's estimates, the single largest crowd the Massachusetts Senator has drawn in her nearly year-long quest to be the 2020 Democratic presidential nominee. (The 15,000 number came from Warren's campaign so take it with a grain of salt. But it's clear from the photos there were a WHOLE lot of people there.)

So, what does crowd size tell us -- exactly?

Well, that depends. Politicos will remember that in the late stages of the 2012 presidential campaign, Mitt Romney was convinced he was going to beat President Obama because -- at least in part -- the size of the crowds coming to his rallies. Romney didn't win -- or even come close.

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