The Iowa caucuses are finally here and Sen. Bernie Sanders (D-Vt) is still holding on to the momentum he’s gained over the last month, with the most recent national polls showing him as the frontrunner.

According to Politico, a pro-Israel Democratic super PAC and a conservative dark-money group have been running attack ads across the state against Sanders, who has responded by staying on message and pushing “Medicare For All, women’s rights, and his movement.”

Pete Buttigieg, former mayor of South Bend, Indiana, leads Sanders by two percent in the latest Focus on Rural America poll—19% to 17%, according to the Hill. Both 2020 hopefuls have gained three points, while former Vice President Joe Biden and Sen. Elizabeth Warren have both gone down in the polls—nine points and three points, respectively. Warren remains the top second choice among voters, with 20 percent of the vote.

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What’s At Stake?

There are 1,679 caucus precincts in Iowa, with Democrats having satellites in Paris, Glasgow, Scotland, and Tbilisi, Georgia. Voters separate into groups in their designated caucus precinct based on the candidate they support. Each person in each group is counted. If the number of people in a group makes up at least 15% of the number of the people in the room, then their candidate is deemed viable.

If a voter’s candidate is viable, they fill out a Presidential Preference Card; if their candidate is not, they have the option to join with a viable candidate or rally support among other voters in the room whose candidate is also not viable.

The final, viable candidates earn delegates, McClatchy DC explains. The formula for determining delegates is: “The number of people in each group, multiplied by the number of delegates the precinct is electing — which is then divided by the total number of caucus attendees.”

According to the Intercept, in the first in-state votes of the Iowa caucuses, 14 pork plant workers unable to attend their caucus later this evening cast votes for Sanders. One worker cast a vote for Warren, which failed to make her viable. The voter elected not to switch her vote to Sanders.

Since 1976, the late Sen. John McCain is the only presidential candidate that went on to win their party’s nomination after not being one of the top three vote-earners in Iowa.

The Iowa caucuses officially begin at 8 p.m. ET.