Huge caucus. Photo: Jim Watson/AFP/Getty Images

Maybe Donald Trump and Bernie Sanders really did attract a wave of new voters into the process. Maybe the unseasonably warm weather — balmy low 40s — has put Iowans of all stripes in a caucusing mood. Or maybe political reporters are just anxious for an exciting story line.

Whatever the reason, Twitter is overflowing with reports of high turnout at Iowa caucus sites:

This Dem precinct ran out of voter registration papers. Much bigger turnout than expected pic.twitter.com/wt1pINYX05 — Betsy Woodruff (@woodruffbets) February 2, 2016

Crazy amounts of new registrations at GOP caucuses, longtime activists tell me #iacaucus https://t.co/80iP8E6uYI — Jennifer Jacobs (@JenniferJJacobs) February 2, 2016

CNN reporting #bigturnout at every #Iowacaucus location they cover. That sounds like good news for #Trump and #Bernie. — J.J. Goldberg (@jj_goldberg) February 2, 2016

Turnout is very strong, per longtime Iowa GOP hand in touch w many a precinct. — Jonathan Martin (@jmartNYT) February 2, 2016

"Turnout seems to be good at both Democratic and Republican sites" - Katty Kay #IowaCaucus https://t.co/zWMkGbDUyP https://t.co/tvmE5OMjLb — BBC News (World) (@BBCWorld) February 2, 2016

Turnout is critical in any election, but it’s expected to be an even more important variable in tonight’s close contests. Both Sanders and Trump draw much of their support from potential first-time caucusgoers. The trouble with first-time voters is they’re uniquely liable to become next-time voters. Thus, conventional wisdom suggests that the higher the turnout, the better the chances one or both anti-Establishment candidates will win the night. In the last 24 hours, one poll of the Democratic race had Clinton up by three points; the other had Sanders down by the same amount. The difference? The latter poll projected slightly higher turnout.