Expansion supporters added the measure to a budget bill during the Senate's floor session.
That angered conservatives, including Biggs, who ended up voting against a budget that he had crafted. Biggs and 10 other Republicans voted against all 10 budget bills.
"Mark my words — Arizona will rue this day," said Sen. Steve Yarbrough, R-Chandler.
Republican Gov. Jan Brewer shocked many when she announced in January she wanted to expand Medicaid after opposing Obama's health care overhaul for years.
The bill now goes to House, where its chances are unclear. House Speaker Andy Tobin wants voters to decide the Medicaid expansion debate.
The debate was the first by Arizona lawmakers on Brewer's Medicaid proposal, which has divided the Legislature and led to weeks of stalemate.
The Medicaid plan was added onto a budget bill by Republican Majority Leader John McComish.
The Senate's 13 Democrats supported the plan and five Republicans, including McComish, also backed it.
Biggs and other opponents offered two dozen amendments to the Medicaid plan, including one that would have required a two-thirds vote for passage and another to block a hospital assessment Brewer plans to pay the state's costs.
All but two failed, with senators adopting an amendment forcing the plan to expire on Jan. 1, 2017, and for hospitals to review their uncompensated care after the expansion is in place.
During the debate, Republicans on the losing side repeatedly called on the five who were supporting the bill to change their minds, including state Sen. Al Melvin of Tucson, who said they were putting the state on a track to bankruptcy by embracing "Obamacare."
"We have to stop it, and we have to stop it now," Melvin said. "We were all called to be leaders here today and that leadership means we need to defeat this."
Biggs and other opponents argued that the federal government — what Biggs called "our dubious partner" — could not be trusted to keep its promise of funding the newly insured through Medicaid.
Besides McComish, the Republican senators supporting the Medicaid expansion plan were Rich Crandall, Adam Driggs, Bob Worsley and Steve Pierce.
Brewer argues the expansion will bring in $1.6 billion in federal money a year, help hospital savoid hundreds of millions in free care they're now providing to the uninsured and provide good healthcare for many without insurance.
Biggs is fiercely opposed to expanding Medicaid but was outmaneuvered by expansion supporters in his Republican caucus.
He used every procedural tool in his arsenal as president, including a 30-minute floor speech, to try to prevent the approval.
Before the floor session, majority Republicans debated the issue among themselves during a heated caucus during which GOP Sen. Rick Murphy accused McComish of betraying fellow Republicans by sponsoring the Medicaid amendment.
"There are people of good faith, good conscious, good Republicans, who are on both sides of this argument," McComish told his fellow Republicans. "Let's not disparage them."
McComish's amendment appears to mirror draft language proposed by Brewer.
The House is expected to take up the budget and the expected Medicaid attachment next week.
McComish said he believes the amendment will pass the Senate, then face a more difficult challenge in the House.
"I think there are the votes in the House to pass it," he said Wednesday. "We'll see how it is handled in the House. It has to go through House Appropriations, so there's a lot of steps and therefore a lot of pitfalls along the way."
Sen. Leah Landrum Taylor, the minority leader, said the Senate has done the heavy lifting on the budget and on Medicaid and she hopes the House passes it quickly.
Brewer has made the expansion her No. 1 priority for the annual legislative session.
