Cahill's first attempt to be elected to political office came in 1981, when he unsuccessfully ran for a seat on the Quincy City Council.

[12] Cahill ran as an independent for the office of governor of Massachusetts, with former State Representative Paul Loscocco (R) as his running mate.

He ran against incumbent Governor Deval Patrick (D) and the former Harvard Pilgrim Healthcare CEO Charlie Baker (R).

A Boston Globe poll, published on September 26, 2010, showed Cahill to be drawing more votes from Patrick than from Baker.

[13] On October 1, 2010, Loscocco announced he was withdrawing from the race for lieutenant governor and was endorsing Baker although it was too late to remove his name from the ballot as Cahill's running mate.

[15] Cahill ended his employment with Compass on March 7, 2017, shortly after he had paid off his $100,000 civil fine and completed his probationary period from a 2013 settlement with Massachusetts Attorney General Martha Coakley (see next section).

Two days later, Cahill's senior adviser Scott Campbell wrote, "I think the first thing is to figure out what/where/how we want to do this .. with Lottery people."

On April 2, 2012, Cahill was indicted by a grand jury on charges that he used $1.65 million in Massachusetts State Lottery advertising to aid his campaign for governor in 2010.

On December 12, 2012, a mistrial was declared in the corruption case after the jury failed to reach a verdict on two counts of conspiracy.

On March 1, 2013, Cahill agreed to pay a $100,000 civil fine in exchange for the prosecution dropping its criminal corruption case against him.