DOVER — A special election that will decide control of the state Senate has been set for Saturday, Feb. 25.

Lt. Gov. Bethany Hall-Long made the announcement Tuesday while the Senate was in session.

Democrat Stephanie Hansen will face Republican John Marino for the 10th District seat, vacant since Jan. 17, when Lt. Gov. Hall-Long gave up the office to be sworn into her new post.

The Senate currently has 10 Democrats and 10 Republicans.

Democrats have held the chamber for the past 44 years and have controlled the Senate, the House and the governor’s office since 2008.

After the announcement was made one Republican senator could be heard saying “Here we go,” while another remarked, “Let the games begin.”

Ms. Hansen, in a statement, said she was “relieved” the election has been scheduled.

“It’s the number one question I get on doorsteps all across the district and I’m so glad I can finally answer it with certainty,” she said. “Since I joined this race in December, my focus has been on building bridges and bringing hope to voters after a divisive and ugly national political battle that has rattled our communities.”

On Monday, the Republican Party alleged that the Democratic Party had already chosen the date but had not publicly announced it in an effort to discredit Mr. Marino.

“What is the holdup?” Delaware GOP Chairman Charlie Copeland had said in a statement. “The people of the 10th district are without a senator. The Democrats have known about the vacancy since November, and both parties have selected candidates, but a week has gone by and we don’t have a date. What more do they need in order to call for an election?”

Lt. Gov. Hall-Long called the allegation “baseless” but otherwise declined to comment.

By law, she had until Friday to schedule the contest.

The election had to be set between 30 and 35 days after the selection was made.

The district, which covers portions of Newark and Middletown, lists about 16,100 Democrats and 10,100 Republicans, as well as 9,400 independents.