SACRAMENTO — In fighting to block proposed state regulations, Uber Technologies Inc. has embraced the role of fledgling startup, a novel Valley innovator just trying to fend off the big hand of government. This week, however, the San Francisco-based ride-sharing company recently valued at $18 billion has turned to decidedly old-school, hardball politics.

Uber sent mailers to constituents of Assemblywoman Susan Bonilla, D-Concord, the author of the main ride-sharing bill moving this session, accusing the lawmaker of serving as an insurance industry pawn and “leaving consumers and entrepreneurs on the curb.” The notices have also hit mailboxes in a wider Senate district that Bonilla may run for in a future election.