Brian Shortsleeve, a venture capitalist and former MBTA official running a Republican campaign for governor, outraised his potential primary opponent, Mike Kennealy, and Gov. Maura Healey last month, according to state campaign finance records.

More than $848,000 poured into the three campaigns in May, the first month with two Republicans and an incumbent, first-term Democrat officially in the 2026 race for governor of Massachusetts. The candidates also spent a collective $638,000 last month, data showed.

Holly Robichaud, a political strategist for Shortsleeve, said the 52-year-old Barnstable resident proved “he is the only candidate (with) broad base support by even out-raising Maura Healey.”

“He has the strength and determination to win,” Robichaud said in a statement. “To defeat Healey, it takes more than a Kennealy just writing a check. In 20 days, Brian raised four times more than his GOP opponent and outraised the incumbent governor because he has the strong message of restoring affordability for Massachusetts.”

Shortsleeve, who announced his bid for governor May 12, initially reported raising more than $417,000 last month from a swath of business executives like Niraj Shah, the co-founder of Wayfair, and local billionaire Ernie Boch Jr. He refunded a single $1,000 donation to bring his total fundraising haul to $416,000 for the month, data shows.

But state records show he pulled in $321,247 in May, a discrepancy likely caused by the timing of donations to the campaign compared to when Shortsleeve’s bank reported the dollars to the Office of Campaign and Political Finance.

He ended the month with more than $275,000 cash on hand, a sizable sum for a Republican who launched his campaign roughly over a year before the statewide general election in Massachusetts.

Healey brought in the least amount of cash last month of the three declared candidates, raking in just over $236,000 and spending more than $477,000, according to state campaign finance records.

The governor had $3.1 million cash on hand as of the end of May, a massive warchest that dwarfs the bank accounts of the two Republicans in the race, state data showed.

A spokesperson for Healey’s campaign said the governor is “headed into this election with unmatched fundraising strength, widespread grassroots support, and a strong record of delivering for the people of Massachusetts.”

“Voters know she is the candidate they can count on to make the state more affordable, build more housing, and improve education and transportation, while also standing up to Donald Trump when he hurts our residents,” the spokesperson said.

Healey’s largest expense in May was a $383,445 transfer into an interest-bearing money market account and a $40,000 payment to Beacon Research for an internal poll, according to state records.

Kennealy pulled in more than $291,000 last month, a majority of which came through a $200,000 loan the Lexington Republican handed his campaign as part of a pledge to seed his bid for governor with $2 million.

Kennealy’s campaign said it raised $104,000 in May from donors. The discrepancy between what the campaign and state regulators report for fundraising is a result of delays by Kennealy’s bank in handing state regulators data, the candidate’s aides said.

Kennealy’s final tally for last month may also change because of at least five excess donations that campaign officials will need to refund. Massachusetts Democrats called for an investigation into Kennealy early last month after his campaign reported more than 50 over-the-limit donations in April.

He spent $114,651 in May, including $14,000 to the research firm Opinion Diagnostics and $11,333 to the Florida-based fundraising firm Red Beacon Strategies. Kennealy had more than $433,000 cash on hand as of the end of last month, according to Tate data.

Logan Trupiano, a spokesperson for Kennealy, said the campaign has raised more than $630,000 since its inception.

“Mike Kennealy personally invested $400,000, underscoring Mike’s unwavering determination to bring commonsense, pragmatic leadership to Massachusetts. With $433,338.64 cash on hand, we’re leading the primary field and building real momentum — and we’re just getting started,” Trupiano said in a statement to the Herald.