State Treasurer Tim Cahill, Gov. Deval Patrick and their predecessors and rivals have reaped huge contributions from people whose firms do business with the state pension fund, the Herald has found.

A Herald review shows that workers at companies tied to the fund have given at least $1 million since the 2002 election cycle to candidates for treasurer and governor. Those are the two elected officials who appoint members to the fund's board of directors.

Donors include top executives at Fidelity Investments, State Street Corp. and other firms that either had big contracts with the $41 billion pension fund at the time or later bid for business.

"These companies are making an investment in political capital," said Edwin Bender of the National Institute on Money in State Politics. "It's not green money (that donors want). It's the power and influence that elected officials can exert over (pension contracts)."

Big political donations - and sometimes outright kickbacks - have long plagued the public-pension business, where favored companies can reap millions of dollars in investment-management fees.

Bender said firms that hope to befriend governors and treasurers often rely on workers to make donations, as Massachusetts and many other states ban direct corporate giving. Even a few thousand dollars of employee donations can get firms noticed, as workers can only give $500 per candidate each year and can't legally seek company reimbursement.

A Herald review of public records has found that donations to Massachusetts pols have included:

** some $270,000 from employees of Boston law firm Mintz Levin, which has long served as the pension fund's main outside counsel. Donations include more than $70,000 to both Patrick and Cahill, as well as $45,975 to former Republican Gov. Mitt Romney. Mintz staffers also gave $2,525 to Romney's presidential campaign while he was still governor.

** about $166,000 from employees of Fidelity Investments, which oversees part of the pension's "junk bond" portfolio. Romney netted the lion's share of donations ($54,498), followed by $41,175 for former Attorney General Thomas Reilly, a 2006 Democratic gubernatorial hopeful.

** nearly $100,000 from workers at Bank of New York/Mellon, which earned $458,000 in brokerage and custodial fees from the pension fund in fiscal year 2008.