these crowds, people who are all in. >> reporter: perhaps no one cares about crowd size more than the president of the united states himself. >> one thing we know, we get the biggest crowds by far. >> reporter: something that signaled something was going on with the gop field. >> we have these incredible crowds. something is happening that's amazing. >> reporter: especially in contrast with the presumed front-runner at the time. >> please clap. >> reporter: trump is not the first person to translate crowd size into something real. then candidate barack obama drew thousa thousands to then rival hillary clinton. >> reporter: drawing 27,000 to that same park in 2015 but lost the nomination. same question as elizabeth warren rallied her biggest event yet. >> does crowd size matter? >> even though biden is polling