(The Center Square) – U.S. Sen. Jacky Rosen’s seat representing Nevada is now rated as a “toss up” race, according to The Cook Political Report.

Rosen became senator in 2019 after defeating incumbent Sen. Dean Heller, a Republican.

The race could be key in Republicans’ efforts to flip the Senate in November’s election. Republicans currently hold 49 seats and Democrats hold 48, but three independent senators caucus with Democrats, giving them the majority of seats.

Other Senate races that Cook rates as toss ups are in Ohio (Democratic Sen. Sherrod Brown), Montana (Democratic Sen. Jon Tester) and Arizona (Independent Sen. Kyrsten Sinema).

“Experts predict that Nevada could once again decide Senate control and my race is now caught in a statistical dead heat,” Rosen said in a tweet from her campaign account.

Jessica Taylor, senate and governors editor for The Cook Political Report, said the rating change “may be a bit surprising.”

“After all, it’s the only one of the swing states Democrats carried in both 2016 and 2020 at the presidential level, and Republicans haven’t won a statewide federal race here since 2012,” she wrote. “And of the quartet now in Toss Up, it is still probably the toughest.”

Cook assesses races based on competitiveness.

“Competitiveness is determined by several factors, including the state’s political makeup, the candidates’ strengths and weaknesses, the political environment in the state and nationally, and interviews with candidates and campaign professionals,” Cook says on its website.

Nevada’s Democratic primary is on June 11.