Opponents are planning a citizen's referendum that would block the law and a lawsuit is also possible that could be filed as early as Tuesday. To block the law with a referendum, opponents will need to gather more than 86,000 signatures in three months. A successful effort would prevent expansion from going into effect in January and put it on the Nov. 2014 ballot.
"I don't believe it's going to be very difficult at all, said former state Sen. Frank Antenori, a Tucson Republican who is working on the referendum effort. "That's statewide, it's all 15 counties. The Republican party alone has 1.1 million registered voters."
"It wouldn't be Jan Brewer's life if it wasn't for challenges," the governor said after the ceremony. "Today we are celebrating what we've been able to complete and I am very, very grateful for the people that stood with me. And we will just take each day as it comes. I think that overwhelmingly the people of Arizona support us and they will continue to support us in our efforts."
Brewer's staff has said a previous appeals court decision prevents such referendums on appropriations laws, so a court battle could erupt if Antenori's group is successful.
The conservative Goldwater Institute is also considering suing to block the law, arguing that the state constitution requires a 2/3 vote to raise taxes.
Brewer's proposal will impose an assessment or "bed tax" of about $250 million a year on hospitals to pay for the state's share of expansion costs. Neither the House or Senate votes reached that threshold. Goldwater attorney Christine Sandefur said Monday the group may also challenge on a separation of powers argument because the state's Medicaid director is given power to set the assessment and exempt some hospitals.
"In other words, a hospital that has political clout and can get to the director might have that luxury and others will not," Sandefur said.
Any suit could only be filed after the law takes effect in 90 days, she said.
Brewer, an early critic of the Affordable Care Act, surprised the nation when she acknowledged the Medicaid expansion as the law of the land in her State of the State address in January. She noted that rejecting an expansion would mean Arizona taxpayers would subsidize care for those in other states while receiving no benefits themselves.
The expansion is expected bring in $1.6 billion a year in federal funding to help reduce the amount of uncompensated care hospitals must absorb and help cut what Brewer called a hidden healthcare tax that people who buy insurance pay, through higher premiums, to cover others' care.
Conservatives in the Legislature blocked expansion for months, with the Senate finally approving it last month. But the House speaker delayed bringing it up for a vote, and Brewer ran out of patience. She called a special session last week and forced the Legislature to act on an $8.8 billion budget and Medicaid.
At Monday's ceremony, most of the 14 Republicans who backed expansion stood with Brewer and Democrats.
"We will provide healthcare to hundreds of thousands of Arizona's most vulnerable citizens," said Rep. Heather Carter, R-Cave Creek, who chairs the House health committee and backed the law. "And this care will not be in the overcrowded hospital emergency room but in clinics and doctors' office and community health centers across our great state. This is cost-effective medicine, at the right time, in the right setting, saving money and saving lives."
But one member of the coalition noted that their efforts have brought backlash from conservatives. Sen. Steve Pierce, R-Prescott, called the expansion "the right thing to do for Arizona."
"It's a shame that those who disagree with those of us up here are so disagreeable," Pierce said. "We're getting used to it. It's a shame that you can't disagree and disagree honorably and still have discourse. And that's important. That's one thing that's lacking I believe in our Legislature."
