Supporters said it would bolster the state's endangered dairy industry by providing farmers with steadier incomes.
"A lot of farmers can absolutely not afford to stay in business," Derr told the committee.
Sen. Larry E. Haines, R-Carroll, cited statistics showing the retail price of milk has risen 81 cents a gallon from 1984 to 1997, while farmers saw their sale price increase by five cents in that same period.
"It's clear to me that the people who are making the money are not the farmers. It's the retailers," Haines said.
Opponents likened the compact to a Middle East oil cartel that would raise milk prices for consumers while providing minimal relief for farmers.
"This is so basically and simply an absolutely terrible piece of legislation," said Bruce C. Bereano, a lobbyist representing gas stations, convenience stores and other opponents.
Bereano suggested lawmakers who vote for the bill would have to answer to constituents when they must pay more for milk.
Four members of the Senate committee changed their earlier votes and supported the legislation.
Approval by Economic and Environmental Affairs is crucial because the General Assembly's format gives committees great power to get legislation passed or killed.
Still, lawmakers could face a battle when the legislation reaches the Senate floor, possibly as early as today. Derr said 21 senators favor the bill, but 24 votes are needed for passage.
"It's going to be close. It's going to be tough," said Sen. David R. Craig, R-Harford, a bill supporter and member of the committee.
The milk bill has made what many lawmakers consider to be a remarkable recovery since the Senate panel's vote last month.
Last week, the House of Delegates approved an amended version of the bill, which includes a "sunset" clause under which the legislation would go out of effect in two years unless further action is taken.
That made the bill more palatable to some senators on the committee, as did a personal visit last week by Gov. Parris N. Glendening, who supports the measure. Going into the committee hearing, supporters felt they had enough votes to reverse the earlier vote.
"What a difference a week makes," Craig said.