It was, according to her campaign estimates, the single largest crowd that the Massachusetts senator attracted in his near-year quest to run for Democratic president in 2020 (15,000 came from the Warren campaign, so but you can see that there are a LOT of people out there.)
Well, that depends. Politicos will remember that in the later stages of the 2012 presidential campaign, Mitt Romney was convinced he would defeat President Obama because, at least in part, the size of the crowds coming to his rallies. Romney didn't win – or even approached.
On the other hand, the huge crowds that Obama was able to attract – both as a surrogate for other candidates in the 2006 cycle and then as presidential contender in 2008 ̵
Where do the Warren mobs fit into this spectrum between Romney's false positives and Obama's true positive? It's hard to say right now, but here's what we know:
1. The ability to attract 15,000 people to a campaign at the end of August on an off-year basis is quite impressive
2. Crowd size, especially in primary, is generally a consistent indicator of organic energy
When considered in this context, the Warren mobs are almost certainly an indicator of the real inertia and excitement surrounding her candidacy. No . no matter what any of her rivals behind closed doors (or publicly) can say about what Warren's crowd means (or doesn't mean), you can be sure that each of them would LOVE to be able to draw numbers that the Massachusetts senator is right now.
Point: Yes, August 2019, not February 2020. But Warren is on the main roll – and the size of his ballooning crowd is a reflection of that momentum.