Story highlights Hillary Clinton and Bernie Sanders are fighting over trade, looking to win blue-collar and labor voters

The Michigan primary is Tuesday

Washington (CNN) Hillary Clinton and Bernie Sanders are in Michigan this weekend, home to blue-collar Democratic and labor voters concerned about the future of manufacturing jobs in the state.

And head of CNN's Democratic debate in Flint on Sunday night and Tuesday's primary, a full-fledged trade war has broken out.

Sanders, hoping to exploit what could be a major weakness for Clinton in labor-heavy states, called Clinton the "outsourcer-in-chief," latching Clinton to her husband's promotion of the North American Free Trade Agreement and her slow-to-the-game opposition to the Trans-Pacific Partnership. Clinton is hitting Sanders for siding with Republicans last year in a vote opposing the Export-Import Bank.

They're both playing to a labor-heavy audience, and both attacks get at the core of each candidate's critique of the other: that Clinton sways with the political winds, and that Sanders is too pie-in-the-sky to embrace the tools that deliver actual benefits to real people.

Clinton had dropped her attacks against Sanders in recent days after her dominant win in South Carolina and successful Super Tuesday, turning her attention to Donald Trump, the GOP and the general election. But she is now exchanging barbs with the Vermont senator and self-described democratic socialist.

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