How many ways can you measure the first quarter of the year? For American Democratic presidential candidates, it's 300-plus events, 24 states and hundreds of voter questions.

The Iowa caucus is still 10 months away, but the Democratic primary campaign is already an all-out sprint — passing eye-popping markers for campaign activity and voter engagement. Voters in Florida and Ohio may not see it, but weekends in Iowa, New Hampshire, Nevada and South Carolina — not to mention a handful of select states — are a blitz of candidate rallies and local meet-and-greets.

For some candidates the frenetic pace is the message, a way of casting themselves as tireless and willing to take every last question. Elizabeth Warren and Beto O'Rourke are trying to make an ambitious schedule and accessibility part of their brands, but Cory Booker and Kirsten Gillibrand have done their parts to keep up with several dozen events each, most in early-voting states.