BOLSTERED BY A $150,000 donation from developer John Fish, a super PAC affiliated with Gov. Charlie Baker reported on Monday that it raised $652,500 since late August and spent more than $525,000 on 29 candidates, all but three of them Republicans.

Even though Republicans control only four seats in the Senate, the Massachusetts Majority PAC chose not to support Republican Sen. Dean Tran of Fitchburg, who is facing a challenge from Democratic political newcomer John Cronin. Cronin has been hammering Tran over the Senate’s decision in March to strip the senator of his leadership position and boot him from his office for using State House staffers to do campaign work.

The Baker-affiliated PAC is supporting two other Republican senators facing Democratic challengers – Sen. Patrick O’Connor of Weymouth, who is running against Meg Wheeler of Cohasset, and Sen. Ryan Fattman of Sutton, who is running against Christine Crean of Milford. The PAC spent $35,209 on direct mail campaigns supporting each of the Republican senators. The fourth Republican senator, Minority Leader Bruce Tarr of Gloucester, is running unopposed.

The PAC also spent $30,538 on direct mail advertising supporting Republican Matthew Kelly of Franklin, who is running against incumbent Democratic Sen. Becca Rausch of Needham. The PAC did not support three other Republicans — John Cain of Southwick, James McMahon III of Bourne, and Steven Hall of Sturbridge – running against incumbent Senate Democrats.

Paul Craney of the conservative Massachusetts Fiscal Alliance said the absence of support for Tran’s candidacy caught his attention. “Perhaps the most surprising fact is that Dean Tran is not on your list, considering he’s 25 percent of the Republican Party in the Senate and he’s one of the few minorities in the chamber,” Craney said.

Although the Baker PAC has gained attention in the past for its backing of candidates from both parties, the information released on Monday indicated the PAC is currently only backing three non-Republicans – Democratic Rep. Jerald Parisella of Beverly, who is running against Euplio Marciano, an unenrolled independent; Democrat Thomas Hoye, who is running for register of probate in Bristol County against independent Melanie Layden; and independent Rep. Susannah Whipps of Athol, who is running against Democrat William LaRose.

Of the 26 Republicans the PAC is supporting, 16 are incumbents and 10 are challengers, most of them vying for open seats.

In addition to Sens. O’Connor and Fattman, the incumbents include Norfolk County Sheriff Jerry McDermott (nearly $110,000 spent on his behalf) and Reps. Brad Jones of North Reading ($13,841), David DeCoste of Norwell ($13,410), Donald Berthiaume of Spencer ($13,368), Fred Barrows of Mansfield ($12,531), James Kelcourse of Amesbury ($13,086), Leonard Mirra of Georgetown ($14,696), Marc Lombardo of Billerica, ($12,655), Nick Boldyga of Southwick ($12,961), Paul Frost of Auburn ($12,699), Sheila Harrington of Groton ($13,984), Timothy Whelan of Brewster ($14,124), and William Crocker of Barnstable ($3,125).

Stephanie Fattman, the register of probate in Worcester County, who is facing a challenge from long-time employee John Dolan III, received $5,125 from the Baker PAC.

In addition to Kelly, the other challengers being supported by the PAC include Nancy Stanton-Cross, who is running for county commissioner in Bristol County ($49,071 spent on her behalf,) and state rep candidates John Simmons of North Attleborough ($12,997), Kelley Dooner of Taunton ($11,359), Mathew Muratore of Plymouth ($14,413), Kelly Pease of Westfield ($12,033), Steven Xiarhos of Barnstable ($13,801), Susan Smiley of Lancaster ($12,935), Thomas Ardinger of Leominster ($11,805), and James Harrington of Ludlow ($12,138).

The Massachusetts Majority PAC has no restrictions on who it can raise money from or how much they can donate. Fish donated $150,000 on October 22, which brought his total contributions to the PAC to $200,000.

Other big donors since late August included James Mooney III of the Baupost Group and his wife, who each donated $50,000; Niraj Shah, the CEO of Wayfair, who donated $25,000, bringing his total contributions to the PAC to $75,000; and auto dealer Daniel Quirk, who donated $25,000, bringing his total to $75,000.