The battle over the teacher tenure bill is the latest in a long-running war between the Florida teachers union and conservative Republicans.
Led by former Gov. Jeb Bush, the conservative side of the GOP has long sought to marginalize teachers' unions in Florida, which merged in 2000 to form the Florida Education Association.
Non-partisan but Democratic-leaning, it is Florida's largest and most politically powerful union, with about 140,000 members, including 100,000 of the state's 175,000 public schoolteachers.
Bush wanted to be known as Florida's "education governor," but his reform proposals, including private school tuition vouchers, more standardized testing and state-mandated merit pay plans, have put him at odds with the FEA. He has openly expressed his desire in the past to undercut its clout.
Key allies including state Sen. John Thrasher, sponsor of SB 6, the teacher tenure bill, and Marco Rubio, former House speaker now running for the U.S. Senate, helped push his initiatives through the Legislature - some seemingly aimed as much at the union as at reform.
SB 6 would abolish multiyear contracts for future teachers, base raises largely on student performance on standardized tests, and eliminate experience as a qualification for raises.
It passed on near-party line votes by the Republican legislative majorities.
But Gov. Charlie Crist, a fellow Republican who has clashed with Bush and is now battling Rubio in the Senate primary, is wavering in his support. He must sign or veto it by Friday.
Even Rubio seemed to waver in an interview today, saying in a Tampa radio interview he thinks legislators should fix problems in the bill, and declining to say whether he would sign it.
Bush, the most popular Republican in Florida since Crist's collapse in polls, initially stayed out of the public eye after Crist replaced him as governor in 2007.
Recently, he has become more outspoken, and SB 6 is the state issue he talks about most, often through his education think tank, the Foundation for Florida's Future.
SB 6 is also the hardest hit yet against the union.
"SB 6 is different ... clearly the most direct assault," said state Sen. Dave Aronberg, D-Greenacres, who's running for attorney general. "This one would remove their power to collectively bargain. It's a missile aimed right at the FEA."
FEA President Andy Ford acknowledged the union supports Democrats far more than Republicans.
Asked why, he said, "Their respect for unions and collective bargaining, civil and human rights. They're more willing to fund education, and they're not anti-public school employee."
A check of state records showed FEA political committees have given more than $550,000 to the state Democratic Party since 2000, and $1,700 to the Republican Party.
They also gave to scores of Democratic candidates and causes, while giving to far smaller numbers of Republicans.
Ford said that money comes from voluntary contributions to the committees. Union dues - $400 to $800 a year depending on the county portion - pay for publicizing union stands to members, but not for political activity.
A voucher program moving students out of public schools could shrink FEA's membership base; so could legislation that cuts its ability to bargain for members' pay.
Thrasher and Patricia Levesque, director of Bush's foundation, denied that the foundation was involved in writing or shaping SB 6, although Levesque acknowledged it is consistent with the foundation's emphasis on accountability.
Thrasher denied it's aimed at eliminating collective bargaining.
If the bill passes, he said, the union will still negotiate the size of raises that will be determined by student testing, along with other employee benefits. "They'll still have a role," he said.
"To say Republicans aren't as sensitive to educating our children as Democrats is a gross misstatement," he added. "Where we differ is accountability measurement and choice."
Bush's battle with the union began in earnest when he ran for governor in 1994, espousing an agenda of conservative change, including vouchers. The two unions that eventually merged to form the FEA opposed him.
On Halloween just before the election, teachers dressed as Grim Reapers drove a stake through his education proposal, according to a newspaper report.
After his narrow loss to Democratic Gov. Lawton Chiles, Bush started his foundation and a charter school in Miami.
In 1998, he won the governor's office. With Thrasher as House speaker during his first two years, Bush passed a sweeping agenda included the A-Plus Plan - grading schools based on the results of standardized testing - and a statewide voucher plan.
But the state Supreme Court later ruled the voucher plan violated the state Constitution's prohibition against using public money to aid religious institutions.
Two smaller plans survived, one for disabled students and one giving corporations a tax credit for donating money for private school tuition.
While he was in office, Bush's foundation merged with the James Madison Institute, a conservative, anti-union think tank that included in its newsletter a "Florida Teacher Union Watch," publicizing cases of misconduct by union teachers.
In 2002, the FEA sought to unseat Bush. It spent more than $2 million - more than double its normal annual political spending - backing Tampa lawyer Bill McBride, husband of this year's Democratic gubernatorial candidate Alex Sink.
Late in the campaign, Bush, speaking to a group of legislators and unaware that a reporter was taping his comments, announced jokingly that he had "devious plans" on education.
One, he said, would frustrate the intent of the constitutional amendment limiting public school class sizes, which the FEA strongly backed but critics said was simply an employment measure for teachers.
Another would undercut the FEA's collective bargaining power by imposing a pay plan controlled largely by state officials - which critics say SB 6 will do.
Bush said he didn't want to explain the plan publicly during the campaign because it was a "philosophical reversal" of his often-stated goal of local control of schools.
He easily defeated McBride, and the FEA faced continuing assaults from the Republicans controlling state government:
• In 2001, Bush had pushed through a plan to provide all teachers an $850 bonus, bypassing collective bargaining.
• Bush sought unsuccessfully to offer teachers free professional liability insurance. That would undercut FEA recruiting, because the union also offers free insurance to dues-paying members.
• GOP legislators unsuccessfully sought to prevent the FEA from collecting dues by paycheck deduction.
• In 2007, after he had left office, Bush allies sought to reverse the Supreme Court decision against his voucher program.
• Rubio, then House speaker, appointed Levesque to the state Taxation and Budget Reform Commission, where, with support from other Bush allies appointed by Rubio, she successfully proposed a constitutional amendment that would weaken the prohibition on aid to religious institutions.
The FEA and others sued and blocked the amendment from the ballot.
Regardless SB 6's fate the battle isn't over.
Aronberg said conservatives consider this election year an ideal chance to move their agenda.
"There's a sense of urgency I haven't seen before," he said. "It's unfinished business for Jeb Bush."