Fox News contributor Mara Liasson told viewers Wednesday on “Special Report with Bret Baier” that Democratic presidential candidate Bernie Sanders' victory in Tuesday’s Michigan primary sent a clear message to challenger Hillary Clinton about her viability in key states in the general election.

“Sanders now says, look I'm winning in the states that are actually battleground states in the fall, she's winning in red states that don't really matter, you know, in the general election. So, he has...that was a huge, huge thing that happened last night,” Liasson, a National Public Radio national political correspondent, said.

Sanders pulled off an upset in Michigan, winning by a slim margin, 49.8 percent to Clinton’s 48.3 percent. 

Liasson noted “that was not expected, wasn't even expected by Bernie Sanders, he looked as stunned as anybody else did,” adding that Sanders’ victory in a state like Michigan could have much larger implications for Clinton later on, should she secure the nomination.

"He won in a state where the Democratic primary electorate resembles the national electorate much more than in South Carolina or Mississippi," Liasson said, pointing to two of Clinton's recent victories.

“And the question this raises is, if she can get beat by a Democratic populist in Michigan in March, why can't she get beat by a Republican populist in Michigan in November?"