Should he make an official announcement soon, Rafferty, 58, of Lower Providence, would become the first Republican to put his name in contention amid a growing field of Democratic candidates.
Former U.S. Rep. Patrick Murphy of Bucks County, Philadelphia lawyer Dan McCaffery, and Lackawanna County prosecutor Kathleen Kane have all publicly said they intend to run in their party's primary.
Although the names of several likely contenders have emerged on the GOP side - including that of Montgomery County District Attorney Risa Vetri Ferman - none has made a decision public. Cumberland County District Attorney David Freed has come closest, floating the idea of his own candidacy at a party meeting in May.
Interim Attorney General Linda L. Kelly has said she will not seek election to a full term. She replaced Corbett earlier this year, when he resigned to become governor.
"There's no heir apparent on either side. We could have a crowded field," said G. Terry Madonna, a pollster and political analyst at Franklin and Marshall College. "I think the attorney general's race at the moment is still fairly wide open."
The emergence of a Rafferty candidacy suggests the odds of Ferman entering the race are less likely, party insiders said Tuesday. Both are known as cautious campaigners, and a primary with two candidates from Montgomery County could split the region's vote, they said. Both would be looking to the same factions in party leadership for support.
Although many had seized on Ferman's growing campaign coffers - more than $266,000 as of her last finance report in June - as a sign she might make a statewide run, she said in June she was focused on winning reelection this fall. She faces no opponent in that race.
According to his latest campaign reporting, Rafferty had about $100,000 in campaign contributions on hand as of June.
First elected to the Statehouse in 2002, he previously was a deputy attorney general from 1988 to 1991.
Contact staff writer Jeremy Roebuck at 267-564-5218, email@example.com, or @inqmontco on Twitter. Read his blog, "MontCo Memo," at www.philly.com/montcomemo