NEWYou can now listen to Fox News articles! MADISON, Wis. – For a second straight week, the Midwest is the key battlefield in the high-stakes fight between the left-wing and the center-left establishment for the future of the Democratic Party.After far-left candidate Abdul El-Sayed narrowly edged out more moderate Rep. Haley Stevens a week ago in battleground Michigan’s Democratic Senate primary, which was the biggest stage to date in the party’s ideological civil war, the spotlight now shifts to statewide nomination showdowns Tuesday in Wisconsin and Minnesota.At stake: a top-tier Senate showdown in Minnesota that’s among a dozen races nationwide…