Auto insurance rate legislation backed by a major campaign contributor has been approved by the state Senate despite opposition from consumer advocates and the state insurance commissioner. The bill would allow an insurer to offer discounts to customers who have a record of maintaining auto coverage with another company.

Current state regulations allow insurers to offer so-called loyalty discounts to their longtime customers, but not to new customers with a record of keeping up their coverage with a competitor.

Critics say the bill is being pushed by Mercury Insurance because the company wants to be able to use such discounts to lure middle-class customers away from competitors.