Supermarkets and big-box stores could sell cheap gas and discounted prescription drugs under a bill that won the Senate's initial backing Tuesday after a bruising floor flight.

"Competition in our society always benefits the consumer," said the bill's sponsor, Sen. Steve Johnson, R-Fort Collins. "It doesn't make sense to try to restrict healthy competition."

But opponents fear the bill will help giant retailers such as King Soopers, Safeway and Wal-Mart seize the market and drive convenience stores and independent petroleum distributors out of business.

They assailed a weekend campaign on behalf of the bill. The Colorado Retail Council distributed hundreds of fliers in front of King Soopers, Safeway and even at one lawmaker's church Sunday that warned "powerful interests are working overtime" to stop Coloradans from saving money at the pump.

"This bill strikes a vulnerable core - cheap gas and cheap drugs," said Sen. John Morse, D-Colorado Springs, who led an unsuccessful effort to defeat it.

In a separate effort, House Bill 1208 would allow retailers to sell deeply discounted gas and low-cost prescription drugs through customer loyalty programs. The bill is sponsored by Rep. Cheri Jahn, D-Wheat Ridge.

The bill was introduced after small gas stations, citing the state's predatory pricing law, last year won a $1.4 million court judgment against King Soopers for giving gas discounts to customers who bought groceries.

Colorado is one of nine states that prohibits the sale of gas below cost. The bill would allow the stores to bundle grocery prices and gas prices under a formula that avoids violating the law.

The measure sailed through the House but hit trouble in the Senate. Some rural and Front Range lawmakers teamed to try to kill the bill. The bill has passed the House.

washingtonam@RockyMountainNews.com or 303-954-5086