MADISON, Wis. — The Wisconsin State Patrol was dispatched today to find a Democratic state senator who fled the Capitol to delay the near-certain passage of a bill to end a half-century of collective bargaining rights for public workers, a measure that’s attracted thousands of protesters for four days.

With Democrats saying they won’t return before Saturday, it was unclear when the Senate would be able to begin debating Gov. Scott Walker’s measure meant to ease the state’s budget woes. Democrats who disappeared Thursday at first kept their whereabouts secret, then started to emerge to give interviews and fan the protests.

Senate Republicans convened briefly this morning to renew a call to find the Democrats, then recessed. Senate Majority Leader Scott Fitzgerald, R-Juneau, told reporters he has asked the governor to send two state troopers to Senate Democratic Minority Leader Mark Miller’s suburban Madison home. He said he believes Miller may be there – he did not elaborate on why he thought that – and Walker agreed to dispatch the officers.

The Wisconsin Constitution prohibits police from arresting state lawmakers while the Legislature is in session, except in cases of felonies, breaches of the peace or treason. Fitzgerald said he’s not looking to have Miller arrested, but he wants to send a signal about how serious things are becoming in the Capitol.

Fitzgerald said he spoke with Miller by phone late Thursday night and asked him to bring his caucus back to Madison for a vote this morning, but Miller refused. Meanwhile, the protests are growing so large that Capitol workers and lawmakers’ staff cannot safely move through the halls, he said.

The situation has become “a powder keg,” he said.

“I’m starting to hold Sen. Miller responsible for this,” Fitzgerald said. “He shut down democracy.”

The protests have attracted teachers, grade school children, college students and other workers over four days. Police report they have been largely peaceful, with only nine people cited for minor acts of civil disobedience as of Thursday night.

While the Senate was paralyzed, the Assembly met briefly today. Speaker Jeff Fitzgerald, R-Horicon, said the Assembly would vote on the bill later in the day after Democrats have had a chance to meet privately.

Assembly Minority Leader Peter Barca vowed to fight to the “bitter end,” in a speech delivered on the Assembly floor after Republicans had turned off the microphones and left.

“This is wrong!” Barca shouted to wild applause from the packed gallery. “Desperately wrong and we will not stand for it!”

Several hundred protesters were in the building early in the morning. The ranks grew as the day progressed. Many of them spent the night in the Capitol and another large rally was planned around noon.

As many as 25,000 students, teachers and prison guards have turned out at the Capitol this week to protest, standing shoulder-to-shoulder in the building’s hallways, sitting cross-legged across the floor and making it difficult to move from room to room. Some brought along sleeping bags and stayed through the night. Union organizers expected yet more to gather Friday.

The protesters chants of “Kill the Bill!” and “Recall Walker Now!” could be heard throughout the day and long past dark. They beat on drums and carried signs deriding Walker and his plan to end collective bargaining for state, county and local workers, except for police, firefighters and the state patrol.

Hundreds of teachers have joined the protests by calling in sick, forcing school districts – including the state’s largest, Milwaukee Public Schools – to cancel classes.

Despite the groundswell of support, it seems Democrats are merely delaying the inevitable – Republicans say they have the votes to pass the bill – yet the protesters are undeterred.

In an interview with Milwaukee television station WTMJ, President Barack Obama compared Walker’s bill to “an assault on unions.”

Senate Republicans planned to try for a vote again today. With 19 seats, they hold a majority in the 33-member chamber, but they are one vote short of the number necessary to conduct business. The GOP needs at least one Democrat to be present before any voting can take place. The measure needs 17 votes to pass.

Speaking on CBS’ “The Early Show” this morning, Walker urged the Democrats to return to Madison and face the vote.

“The state senators who are hiding out down in Illinois should show up for work, have their say, have their vote, add their amendments, but in the end, we’ve got a $3.6 billion budget deficit we’ve got to balance.”

Senate rules and the state constitution say absent members can be compelled to appear, but it does not say how.

The proposal to eliminate collective-bargaining rights marks a dramatic shift for Wisconsin, which passed a comprehensive collective bargaining law in 1959 and was the birthplace of the national union representing all non-federal public employees.

The legislation also would make public workers pay half the costs of their pensions and at least 12.6 percent of their health care coverage – increases Walker calls “modest” compared with those in the private sector.

Republican leaders said they expected Wisconsin residents would be pleased with the savings the bill would achieve – $30 million by July 1 and $300 million over the next two years to address a $3.6 billion budget shortfall.