Cambridge election officials kicked off a recount Thursday morning in the race for a House seat held by Rep. Marjorie Decker, a six-term Democratic incumbent who faced a challenge from local organizer Evan MacKay.

The race between MacKay and Decker came down to the wire last week during the state’s Democratic primary election, with MacKay initially leading Decker by tens of votes and reportedly declaring victory.

But updated tallies released by the city’s election department flipped the script and put Decker ahead by 41 votes.

Hours into the process, dozens of people were still hand-counting votes in a Cambridge community center.

A small army of election workers cracked open boxes of ballots and methodically reviewed them before moving on to the next precinct. Challenged ballots were brought to a table of commissioners who would make a final call on the vote.

Decker and MacKay’s Democratic primary stood in stark contrast to the vast majority of contests for incumbents on Beacon Hill who were expected to glide to reelection because they faced no opponent during the general election in November.

The outcome of Thursday’s recount is also likely to decide the race for the Cambridge-based House seat because there is no Republican running for the post.

Decker declined to comment on the recount as she walked out of the Russell Youth Community Center.

MacKay has described themself as a pro-democracy organizer and a teaching fellow at Harvard. They have pointed to transparency in government, climate, housing, “progressive taxation,” and taxing the ultra-wealthy as key priorities.

Decker has spent the past two decades-plus in the Massachusetts House and serves as the co-chair of the Public Health Committee.

She successfully negotiated a maternal health bill this summer with Senate counterparts and has pointed to gun safety, labor and workers rights, and criminal justice reforms as key issues she has focused on in the Legislature.

The recount underway Thursday served as a major test to political incumbency in Massachusetts, an often unbreakable power that has fueled decades-long careers at the State House.

Decker and MacKay’s recount is not the only one in Massachusetts following last week’s primary elections.

The Republican primary between Rep. Matt Muratore of Plymouth and Kari MacRae, a Bourne School Committee member, for a South Shore and Cape Cod Senate seat also culminated in a recount.

In a statement Wednesday night, Muratore said his campaign “has shifted its focus to November.”

“In the spirit of this confidence, our campaign will respect the recount process, and we work collaboratively with election officials to ensure that the intent and will of every voter is properly discerned,” he said. “We now, however, are solely focused on Dylan Fernandes and ensuring that his dead wrong and dangerous ideas remain far away from the state Senate.”

In a post to social media Wednesday night, MacRae said the race was not called after an initial review of ballots but her campaign “picked up four votes overall.”

“Long day, but very successful,” she said.

This is a developing story…