Michigan voters head to the polls Tuesday in a Democratic Senate primary that could reshape the party, with populist Abdul El-Sayed and Rep. Haley Stevens leading the field. El-Sayed has questioned the assumption that Michigan voters are moderates, a central debate in a race that will test the party's direction. Stevens, a sitting congresswoman, and El-Sayed, a former Detroit health official, are the top contenders for the Democratic nomination. On the Republican side, former Rep. Mike Rogers runs unopposed for the GOP nomination, setting up a likely general-election matchup. The primary outcome will signal which wing of the Democratic Party holds sway in a key Midwestern battleground state.