Senate Republicans are in line to see one more member added to their ranks this session after Rep. Peter Durant declared victory Tuesday night in a special election for a Central Massachusetts seat that includes Gardner and a sliver of Worcester.

Political onlookers have largely viewed the race between Durant and Democratic Rep. Jonathan Zlotnik as a test of the MassGOP’s new leadership’s ability to grow the party’s legislative strength in the wake of former Chairman Jim Lyons’ departure.

The test proved successful in this election, where a Democratic seat was flipped to the Republican column.

Durant declared victory just after 9 p.m. at an election night party in Rutland.

“I look forward to representing your values and interests on Beacon Hill,” he said on social media. “To my wife, Kate, thank you for your constant support, especially over the past five months. I owe this all to you. I look forward to sharing more information with you in the coming days as I look forward to continuing to represent Central Massachusetts in Boston.”

Zlotnik said he conceded to Durant after speaking to supporters in Gardner. Zlotnik said he plans to run for his House seat again in fall 2024.

“We knew all along that this was going to be a tough race. This is a tough district. I think it’s fair to say that Democrats are facing headwinds,” Zlotnik said by phone just before 10 p.m.

Unofficial results poured in fast after polls closed at 8 p.m. with Durant winning many of the municipalities in the district, including his own hometown of Spencer by more than 520 votes.

But it was the key cities of Gardner and Worcester that seemed to be the nail in the coffin. While Durant lost both to Zlotnik, the difference in votes was enough to help Durant carry the rest of the Senate district.

Durant managed 1,511 in Gardner compared to Zlotnik’s 1,869, and 1,056 in Worcester compared to Zlotnik’s 1,572, according to data from both clerks’ offices.

Zlotnik said he was expecting a higher turnout in both cities.

“That just didn’t happen,” he said. “That was a big factor. And I haven’t seen the actual numbers broken down precinct by precinct yet, but I did notice that the turnout was lower than we were expecting.”

Durant succeeds Anne Gobi, a Democrat who left the Legislature earlier this year to serve as the director of rural affairs in the Healey administration.

The Spencer Republican defeated Bruce Chester in a special primary election last month, and with Tuesday’s win, Durant will face reelection next fall.

Durant focused much of his campaign on the influx of migrants arriving in Massachusetts, the strain on the emergency shelter system, and a call to repeal a decades-old law that requires the state to provide temporary housing to homeless families with children and pregnant women.

But he said economic development in the Senate district also proved to be an important issue among voters.

“We have old mill towns like a lot of Massachusetts,” he told the Herald earlier in the day. “We have a large number of farms here in the district. So those kinds of issues come up, as well as regional school issues that we see. It’s one of the largest districts with regional school districts covering most of those towns.”

Durant also received endorsements from former Republican Gov. Charlie Baker and Lt. Gov. Karyn Polito.

Zlotnik said rural development and housing issues also played a large role in his campaign.

“That’s been the top thing,” he said. “It’s kind of an umbrella term because some of that has delved more into economic issues or the underlying infrastructure issues that come into place with that.”