UPDATE: Bernie Sanders stuns Hillary Clinton in Michigan primary

With about half of the state's precincts reporting at 10 p.m., Bernie Sanders and Hillary Clinton were running neck and neck in Michigan's Democratic primary.

If Sanders wins, it would be a stunning upset. Clinton was leading by double digits in pre-election polls, and Nate Silver's fivethirtyeight.com website gave her a 99 percent of winning Michigan earlier today.

Clinton was leading in southeast Michigan, while Sanders was running up large margins in most other counties.

Meanwhile, Clinton won today's Mississippi primary.

Earlier in the night, Donald Trump won the Michigan GOP primary.

Michigan has been seen as a critical race for the Sanders campaign, to prove it can be compete in larger, more racially diverse states. Sanders' victories to date have occurred in more rural states that are overwhelmingly white.

Both Clinton and Sanders spent considerable time campaigning in Michigan, focusing on the Flint water crisis as well as other topics. On Sunday, the two participated in a televised debate hosted by CNN in Flint, and on Monday, they appeared in a town hall event held in Detroit hosted by Fox News.

Nationwide, the Democratic Party has 4,763 delegates in play this election cycle, with 2,382 needed to win the nomination. Going into today's election, Clinton had 1,130 and Sanders had 499, including superdelegates.

Michigan has 130 Democratic delegates and Mississippi has 36 that will be awarded proportionally based on today's vote.

Clinton was at a campaign rally in Cleveland this evening, while Sanders is campaigning in Miami. Florida and Ohio are holding their Democratic primaries on March 15.

Julie Mack writes for MLive.com. Email her at jmack1@mlive.com, call her at 269-350-0277 or follow her on Twitter @kzjuliemack.

MORE: Coverage of the 2016 Michigan primary