The secretary of state's office has already mailed out almost 950,000 ballots in advance of the Sept. 1 primary election, representing nearly a quarter of the state's 4.5 million registered voters.

The new data comes as the United States Postal Service faces increased scrutiny over whether or not it will be able to deliver mail-in ballots on time for local clerks to count them. USPS officials warned states in July that deadlines for requesting and casting mail-in ballots are incongruous with the Postal Services' delivery standard.

Secretary of State William Galvin said about 149,000 ballots have been returned to local clerks and he expects mail-in voting will help boost participation while taking into account public health guidelines. The state's top election official said "a lot of people" who requested ballots were primarily motivated by voting in the November general election, adding that more than a million people have asked for ballots for the fall general election.

"This has been a very tedious effort to get all these ballots out. It was a very large mailing, and it had a great response, but it required a great deal of work at the local level to put these ballots out especially in a timely way," he said at a Tuesday press conference.

Galvin also reminded votes that they can still vote in person.

"In fact, I would suggest to you that it'll be safer than going to many supermarkets," he said.