PHOENIX - Thousands of Arizonans receiving health care through Medicaid could be thrown out of that program under one alternative offered by opponents of the governor's plan to expand coverage.

Senate President Andy Biggs, who joined a rally of Medicaid-expansion critics, vowed to do all he can to prevent a vote on Gov. Jan Brewer's proposal to expand coverage to those making up to 138 percent of the federal poverty level, with the state share of the increased cost coming from a special assessment on hospitals.

Biggs' position gives him vast powers to sideline legislation.

Other speakers outlined their objections.

"We have a choice: More socialism and bigger government or more freedom and fiscal stability," said Rep. Warren Petersen, R-Gilbert, one of the leaders of an ant-expansion rally on the Capitol lawn.

Sen. Kelli Ward, R-Lake Havasu City, called the care provided under Medicaid "substandard," and said entitlement programs like this "disincentivize the poor from improving themselves."

Rep. Justin Olson, R-Mesa, said an expanded Medicaid program means more tax dollars for family-planning services would be paid to Planned Parenthood, which has "this mission of terminating life before it's even born."

"I'm not going to allow late introduction of a bill," Biggs said, pointing out the deadline for that was months ago. And even if what the governor wants does end up at the Senate, whether from a House bill or an amendment to something else, "I never made a commitment I'd put it on the floor" for a vote.

House Speaker Andy Tobin has not taken such an absolute stand. But Tobin said he would not allow a vote in his own chamber on Brewer's plan as it now stands.

The Arizona Health Care Cost Containment System, the state's Medicaid plan, makes coverage available for most individuals below the federal poverty level, about $19,500 a year for a family of three. The federal government provides $2 for every dollar of state funding.

The Affordable Care Act provides federal funding for most of the cost of expanding coverage, which Brewer figures could add about 300,000 people to the AHCCCS rolls, now at 1.3 million.

Biggs, however, said the flaw in her argument is whether the federal government will live up to its side of the bargain and provide the extra dollars for an expanded program.

One of the options presented is to simply no longer provide coverage to childless adults, forcing out an estimated 63,000 recipients who were in the system when enrollment was frozen in 2010, and closing the door on more than 100,000 other childless adults who could become eligible under an expansion.

Brewer, in a letter to legislative leaders, called that option "morally repugnant and fiscally irresponsible." It would not, though, endanger the funds for the rest of the Medicaid program as federal law does not require states to provide coverage to childless adults.

But gubernatorial press aide Matthew Benson said that option ignores the 2000 ballot measure requiring the state to provide free care for everyone below the federal poverty level, including childless adults.

However, two years ago, when Brewer pushed through the freeze on enrolling new childless adults, claiming the state could not afford the cost, her lawyers argued - and the appellate courts agreed - the 2000 measure simply requires the state to fund expanded care with tobacco taxes and Arizona's share of a nationwide settlement with tobacco companies.

The court found any additional funding is a decision for the Legislature to make.

Biggs said there is another option: Have the state alone provide care for all childless adults.

"We have enough money in our 'rainy day' fund," Biggs said, at least for the foreseeable future.

The stalemate on Medicaid is having ripple effects. Most notably, lawmakers cannot adopt a budget for the coming year because how much Arizona needs to set aside for health-care costs depends on whether the state joins the expanded Medicaid program and taxes hospitals to pay the cost.