DETROIT — Gretchen Whitmer, a former leader in the Michigan State Senate, captured the Democratic nomination for governor Tuesday night and will face off against the state’s Republican attorney general, Bill Schuette, in a race that looms as a pivotal test of whether Democrats can reclaim power in a state President Trump won two years ago.
In the race for the Republican nomination for Senate, John James, a businessman and former combat veteran, defeated Lt. Gov. Brian Calley, whose endorsement by the Republican governor, Rick Snyder, was overshadowed by Mr. Trump’s full-throated support for Mr. James late in the contest.
Their victories, reported by The Associated Press, set up deep ideological clashes in state’s most prominent general election races in November. In the contests for both the governor’s office and the Senate, some of the state’s most Trump-like conservatives will square off against two traditional Democrats — and two women — in Ms. Whitmer and the incumbent senator, Debbie Stabenow.
In a sign of Mr. Trump’s looming presence in the midterms, both winners alluded to the president in their acceptance speeches.
“It’s time to start winning again,” said Mr. Schuette, echoing a favorite theme of Mr. Trump’s. “I will not be Governor managing Michigan’s decline into a smaller, less significant state. No, I’ll be a jobs Governor.”
Ms. Whitmer also invoked the president in her address to a raucous crowd in a ballroom at Detroit’s Motor City Casino. “Michigan was the place that people used to move to from all around the world,” she said, adding that at a time when some people want to build walls, “we in Michigan are going to get back to building bridges.”
Michigan’s primary came on a day when five states were conducting voting, including a closely watched special election in suburban Columbus, Ohio, where a Democrat was making a strong run in solidly Republican district. That race was exceptionally close with nearly all the vote counted.
In Kansas, the polarizing secretary of state, Kris W. Kobach, an ardent Trump loyalist, was seeking the Republican nomination for governor after receiving the president’s backing a day earlier. Voters were also choosing primary candidates in Missouri and Washington.
In choosing Ms. Whitmer, Michigan voters opted for a known quantity; a former state legislator, she was first elected to the Michigan House of Representatives in 2000. But though she is an experienced legislator with the support of the party’s leaders, Ms. Whitmer bristled at being characterized as an “establishment Democrat.”
Her refusal to support a “Medicare-for-all” or single-payer health care system caused friction between her and her opponents — a former Detroit health director, Abdul El-Sayed, and a business mogul, Shri Thanedar — but Ms. Whitmer said she was proud to “have the receipts from being on the front line as a progressive.”
In recent days Ms. Whitmer had leaned in to her front-runner status, refusing to mention her primary opponents on the campaign trail and admonishing campaign crowds to not take anything for granted. She travels the state in a large bus marked with her trademark campaign slogan: “Fix The Damn Roads.”
She also claims her message is resonating with female voters in the state. “Gender is a huge strength in this environment right now,’’ Ms. Whitmer said in an interview this week. “Women are turning out in droves. I find Republican women coming up to me saying they don’t like what’s happening in the White House and saying they don’t particularly like their options.”
Mr. El-Sayed, in particular, was touted by some as a insurgent progressive in the mold of Alexandria Ocasio-Cortez, the Bronx-born activist who shockingly defeated a leading Democrat, Joseph Crowley, in a New York City House primary in June. Following her victory, Ms. Ocasio-Cortez came to Michigan to campaign with Mr. El-Sayed, as did Senator Bernie Sanders, who held a rally with him on Sunday.
On the Republican side, the results again reinforced how Mr. Trump has refashioned the party in his own image while playing an influential role in many primary races. Both Mr. Schuette in the governor’s race and Mr. James in the Senate primary were backed by the president.
The president recorded a robocall endorsing both candidates as “Trump guys” that was sent out to Republican voters this week.
“I need you to vote for both — they are very important to our great agenda,” Trump said in the call.
Mr. Schuette has long fashioned himself after Mr. Trump, and he soared in polling once receiving the endorsement of the president.
Mr. Trump shocked the political establishment by winning Michigan in 2016, but recent polling has shown some of his support from independents and swing voters could be evaporating. Democrats have hammered the administration across the state recently for Mr. Trump’s protectionist steel tariffs, which they say are raising prices on everyday goods and hurting Michigan workers.
Republican candidates have stopped short of criticizing Mr. Trump regarding the tariffs, and have instead focused their campaign on the social and cultural issues that unite modern Republicans — such as anti-immigration policies or defunding Planned Parenthood.
“As your governor, I’ll enforce our immigration laws and I’ll ban sanctuary cities in Michigan,” Mr. Schuette said in a recent advertisement that also featured Mr. Trump.
On Tuesday, Michigan voters also selected nominees in key House districts throughout the state.
Voters in the Seventh District again backed Gretchen Driskell, a former mayor and state legislator who unsuccessfully ran for the same seat in 2016. Her win sets up a rematch with Representative Tim Walberg, a Republican who won by almost 15 points two years ago.
In a district crucial to Democrats’ hopes of retaking the House, voters selected an establishment favorite, Elissa Slotkin, as the nominee. Ms. Slotkin, a former C.I.A. analyst in Iraq who served in the Defense Department under President Barack Obama, is a third-generation Michigander who has said she entered the race after being enraged by Republican attempts to replace the Affordable Care Act. She will face the Republican incumbent, Mike Bishop, in race currently rated a tossup.