Montgomery County might have spent as much as $9.6 million in the 2010 Democratic primary if the public campaign financing system proposed by council member Phil Andrews was in place that year, according to an estimate by Finance Director Joseph Beach.

The bill, co-sponsored by the eight other council members, would leverage small individual contributions of up to $150 with a system of matching funds. Andrews (D-Rockville-Gaithersburg), a candidate in the June Democratic primary for county executive, said the intent is to draw more small donors into the political process and enable candidates with limited resources to mount competitive campaigns in council and county executive races.

Beach, speaking for County Executive Isiah Leggett (D), who also supports the bill, offered the estimate at a council hearing Tuesday evening. Beach said it was a high-end figure, based on the assumption that all eligible candidates opted into the voluntary system and received the maximum matching funds available. He also estimated that the 2006 primary would have cost as much as $13 million.

Andrews said Thursday that $8 million per four-year election cycle is a more realistic estimate, and a modest investment at $2 million annually.

“Not a huge amount,” he said.