By Nathan Layne

GRAND RAPIDS, Michigan (Reuters) -Donald Trump was dominating early returns in Michigan’s Republican caucuses on Saturday, a presidential nominating contest he was set to win amid simmering internal turmoil.

With 10 of 13 districts reporting results, Trump was trouncing Nikki Haley, his last remaining rival for the Republican nomination, drawing roughly 97% support, according to a tally reported by the state Republican Party.

The state will be a key battleground in November’s general election, a likely rematch between Trump and U.S. President Joe Biden, a Democrat.

Nearly 2,000 party insiders had registered to participate in the presidential caucus in the western Michigan city of Grand Rapids, where they will choose delegates for Trump or former U.N. ambassador Haley, for the party’s national nominating convention in July.

Republicans will also hold caucuses in Missouri and Idaho on Saturday, among the final contests for Haley to alter the course of the race prior to Super Tuesday on March 5, the biggest day in the primaries, when 15 states and one territory will vote.

With victories in Iowa, New Hampshire, Nevada, U.S. Virgin Islands and South Carolina under his belt, Trump is far and away the frontrunner in the race, with Haley hanging on thanks to support from donors keen for an alternative to the former president.

For this election cycle, Michigan Republicans have devised a hybrid nominating system, split between a primary and a caucus.

Trump won the primary convincingly on Tuesday, securing 12 of 16 delegates up for grabs. He could take all of Michigan’s remaining 39 delegates at stake on Saturday, given that will be up to the roughly 2,000 precinct delegates who form the activist base of the party that leans heavily toward Trump.

“The expectation is that Trump sweeps the delegates from the convention,” said Matt Grossman, a political scientist at Michigan State University. “The activists in the party have been for Trump, but the voters have been for Trump as well.”

The contest in Michigan on Saturday held the potential for confusion and could spawn protests. Internal turmoil has been percolating in the party for months, pitting backers of Michigan’s former Republican Party chair, Kristina Karamo, against the faction of party members who voted to oust her on Jan. 6, and installed Pete Hoekstra as chair.

Hoekstra, who Trump backed as chair, is overseeing the convention in Grand Rapids. Karamo had been planning to chair a dueling convention in Detroit on Saturday, but that was canceled after a Michigan court this week affirmed her ouster and an appeals court denied her request to stay the ruling.

At the convention, precinct delegates split into 13 different caucuses, one for each of the state’s congressional districts. If a candidate wins a majority of votes in a caucus they take all three of its delegates, for a maximum total of 39.

Pro-Karamo party chairs for at least two districts have called for caucus meetings separately from Grand Rapids. However, the results from those are unlikely to be accepted by the Republican National Committee, which last month formally recognized Hoekstra as state party chair.

Hoekstra was the U.S. ambassador to the Netherlands during Trump’s presidency. Speaking to Reuters on the sidelines of the caucus meetings, he said he was confident the Michigan Republican Party would unite around the objective of winning the White House and a U.S. Senate seat up for grabs and retaking the state House.

“There is not a philosophical divide or an issue divide,” Hoekstra said. “This is about getting the party ready to win in November … The focus is on beating Joe Biden.”

(Reporting by Nathan Layne in Grand Rapids, MichiganAdditional reporting by Tim Reid in WashingtonEditing by Ross Colvin, Deepa Babington and Matthew Lewis)