Democrats are hoping to take back control of the Senate majority after Election Day, but to do that they need to defend incumbent Michigan Sen. Gary Peters, who’s facing a fierce challenge from Republican John James. For a state that was crucial to Donald Trump winning the presidency four years ago, Michigan is not only a key battleground state for the White House, it’s vital to Democrats’ attempts to wrestle back control of the upper chamber. But while Democratic presidential nominee Joe Biden is leading polls in the state this fall, Peters is locked in a tight battle with his GOP challenger, with no clear leader. “There is a great deal of energy on both sides because of what’s at stake here,” Peters said in an interview with CNN this week in Traverse City. “It’s incredibly important,” he said. “We have to have a majority in the Senate for our president Biden to be successful.” James, a combat veteran and businessman, lost his 2018 bid for Senate against the state’s other Democratic senator, Debbie Stabenow, by nearly 7 percentage points. James was trailing Peters by 10 percentage points among registered voters in a June survey from The New York Times and Siena College. But a recent survey from the same pollsters showed the two candidates now neck and neck — Peters at 43% support and James at 42% among likely voters. A sizable 13% say they are undecided in that race. GOP strategist Jamie Roe, whose firm Grand River Strategies has done work for James’ campaign, told CNN that “there is a huge opportunity for the Republican party here in Michigan to flip a seat.” James declined an interview with CNN, but the Republican candidate on Fox News Thursday argued that Peters “would be less than a speed bump against the leftist move toward anarchy and socialism.” In campaign ads, James has attacked Peters on his handling of the coronavirus pandemic and called him an ineffective lawmaker, while Peters has touted his bipartisan credentials and environmental record. Michigan was one of three states that delivered Trump the White House in 2016, but two years later, Democrats appeared to have rebuilt the “blue wall” by winning the Senate and governor races and flipping two Trump-won US House districts in the 2018 midterms. Inside Elections with Nathan L. Gonzales, a CNN contributor, rates this year’s Senate race Lean Democratic. Democrats need to pick up four seats to gain control of the US Senate if Trump wins reelection. But if Biden secures the presidency, his party would need to win three seats since his vice president, Kamala Harris, would be a tiebreaker vote in the Senate. Four Republican-held Senate seats are currently tilting toward Democrats, with the GOP favored to flip Alabama, according to Inside Elections. Two Senate races in Iowa and Montana, with Republican incumbents, are toss-ups. For Democrats, losing a second seat could complicate the party’s path to take control of the Senate. “There is no path for a Democratic Senate majority without Gary Peters returning to the United States Senate,” former chair of the Michigan Democratic Party, Brandon Dillon, told CNN. The fight to hold onto the seat has made it one of the most expensive races this cycle, with Peters and his allies spending more than $56 million dollars on ads so far compared to $45 million dollars by James and outside groups backing his campaign. Michigan voters, who have already started casting their ballots, are well aware of the stakes. “Having a blue Senate and blue Congress over the next four years is going to dictate all the legislation that our family cares about,” Freddie Courson, a Democratic voter in Michigan, told CNN. Michigan GOP voter Jeff English told CNN that this is “hugely important to Republicans. If they don’t win the Senate, nothing will get done.” CLARIFICATION: This story has been updated to reflect that Roe’s firm has done work for James.