WASHINGTON, Feb. 27 (Xinhua) -- Voters went to the polls across Michigan, a battleground state, on Tuesday for the 2024 U.S. presidential primary.

In the Republican race, former U.S. President Donald Trump, who remains undefeated so far this year, continues to be challenged by former U.S. Ambassador to the United Nations and former South Carolina Governor Nikki Haley.

Tuesday's GOP primary will determine only a portion of how Michigan's delegates will be awarded while the rest will be decided at a state party convention scheduled for Saturday. Trump has a clear lead over Haley in Michigan polls.

U.S. President Joe Biden does not have a major challenger in the Democratic primary, with Minnesota congressman Dean Phillips polling only in single digits nationally, but some activists are urging Michigan Democrats to vote "uncommitted" in protest of the Biden administration's response to the conflict in Gaza.

The economy is the top issue for 31 percent of Michigan voters, followed by immigration, threats to democracy, healthcare, housing affordability, education, crime, and abortion access, according to a new Emerson College Polling/The Hill survey.

Trump narrowly flipped Michigan, also a Rust Belt state, in the 2016 presidential election, defeating Hillary Clinton by just 0.2 percent. Four years later, Biden won by 2.8 percent, bringing it back to the Democratic column.

The U.S. presidential primaries, extending through June, precede the Republican National Convention in July, where the party's presidential nominee is officially selected by delegates, followed by the Democratic National Convention in August, leading up to the 2024 Election Day on Nov. 5.