Michigan Senate primary: Abdul El-Sayed and Haley Stevens battle for Democratic nomination

Michigan voters head to the polls on Tuesday for a closely watched Democratic Senate primary that has become a test of the party's progressive and moderate wings.

Former public health official Abdul El-Sayed faces US Representative Haley Stevens in the race to replace retiring Democratic Senator Gary Peters.

Recent opinion polls have shown El-Sayed leading the contest, although surveys cited by USA TODAY suggest Stevens could perform better against Republican candidate Mike Rogers in the general election.

El-Sayed has campaigned on policies including reducing the influence of money in politics, increasing economic support for working families and expanding healthcare coverage. Backed by Senator Bernie Sanders, he has rejected claims that he is a socialist.

"I'm not somebody who is a socialist. I believe in capitalism. I just believe that capitalism has to be regulated,” El-Sayed told CNN.

Stevens has highlighted her experience in Congress and her work during the Obama administration, arguing she is the strongest candidate to keep the seat in Democratic hands.

The campaign has become increasingly heated in recent days, with both candidates questioning each other's electability.

President Donald Trump also weighed in on the race, telling reporters: "You have a communist vs a socialist. It looks like the communist is leading."

The Democratic nominee will face Republican Mike Rogers in November in a race expected to play a key role in determining control of the US Senate.