MADISON, Wis. — When Democrats won the governor’s office in Wisconsin, it was one of the party’s most celebrated midterm successes in regaining power in the states. Now Republicans are striking back, moving to slash the power of the new governor even before he takes the oath of office.

Democrats reacted with fury, crowding the halls of the State Capitol in Madison on Monday and accusing the Republicans of trying to undo an election they had lost. It was only the latest such Republican effort across the country to try to use legislative action to counter blows the party suffered at the polls. For Wisconsin, a state that both parties will urgently vie to win in 2020 elections, it was one more sign of the ferocious partisan split that has rippled through the state in recent years.

“It’s a power grab,” said State Senator Jon Erpenbach, a Democrat, before a hearing on the package of bills that includes restrictions on the incoming governor’s ability to shift how public benefits programs are run, and on his authority to set the rules that determine how state laws are carried out. “They lost and they’re throwing a fit.”

The long list of proposals Republicans want to consider also includes wide efforts to shore up their strength before Tony Evers, the Democrat who beat Gov. Scott Walker last month, takes office: new limits on early voting, a shift in the timing of the 2020 presidential primary in Wisconsin, and new authority for lawmakers on state litigation. The Republican plan would also slash the power of the incoming attorney general, who is also a Democrat.