Possible Sen. Brown challenger criticizes transit authority for refusing ads

"Moreover, I have trouble reconciling how Sen. Brown’s public votes would be controversial while advertisements for hard liquor featuring scantily clad women or advertisements heralding the coming of the apocalypse are not," he continued.

Massie was the 1994 Democratic nominee for Massachusetts lieutenant governor, losing to the ticket that was headed by former Republican Massachusetts Gov. Bill Weld. He was born with hemophilia and contracted HIV in a blood transfusion.

Democrats have not settled on a candidate to challenge Brown yet, but with the freshman Republican holding the Senate seat that had been occupied for years by Ted Kennedy, they have already indicated Brown will be a top target in 2012.

Massie's campaign said that the MBTA has not responded to his letter about the Brown ad.