Protesters who have descended on Wisconsin’s Capitol in hopes of halting a Republican effort to end a half-century of collective bargaining rights for public workers steeled themselves for a long fight, buoyed by Democrats’ decision to flee to stall the bill’s near-certain passage.

President Obama compared the bill to “an assault on unions” during an interview this week with a Milwaukee TV station.

Tens of thousands of protestors have flooded the capitol building to protest Republican Gov. Scott Walker’s proposal 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 some school districts to cancel classes.

Senate Republicans planned to try to hold a vote Friday. They hold 19 seats but are one vote short of the 20 votes necessary to conduct business. The GOP at least one Democrat to be present before any voting can take place. The measure needs 17 votes to pass.

But all 14 senate Democrats flew the coop Thursday — keeping their whereabouts secret but later emerging to give interviews and fan the flames of protest.

The runaway lawmakers said they won’t return before Saturday, so it was unclear when the Senate would be able to begin debating the measure meant to ease the state’s budget woes.

“We simply think that if God took seven days to create heaven and earth, then maybe we can take a little bit more time as well,” Democratic Sen. Bob Jauch said.

Clearly frustrated, Walker said the Democrats should come back and do their jobs.

Speaking, 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,” Walker told CBS’ The Early Show on Friday. “But in the end, we’ve got a $3.6 billion budget deficit we’ve got to balance.”

The Assembly also planned to be in session Friday and could take up the bill first if the Senate remains in limbo. Senate rules and the state constitution say absent members can be compelled to appear, but it does not say how.

“We left the state so we were out of the reach of the Wisconsin state patrol, which has the authority to round us up and bring us back to the legislature,” state Sen. Mark Miller told ABC’s Good Morning America from an undisclosed location Friday.

Sen. Tim Cullen said he and other Democrats planned to stage their boycott until Saturday to give the public more time to speak out against the bill.

“The plan is to try and slow this down because it’s an extreme piece of legislation that’s tearing this state apart,” said Sen. Jon Erpenbach, who was with Democratic senators in northern Illinois on Thursday before they dispersed.

Walker called the Democrats’ flight a stunt and said he expected them back at the Capitol in a day or two.

But many protesters at the Capitol saw the case of the disappearing senators differently. School guidance counselor Saunnie Yelton-Stanley called it “brilliant.”

Tens of thousands of 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 have brought along sleeping backs and stayed through the night.

Neil Graupner, a 19-year-old technical college student from Madison, said he was planning to stay until the matter is settled.

“The fact that the Democrats have walked out, it shows they’re listening to us,” he said late Thursday as he prepared to spend the night at the Capitol.

Some Democrats elsewhere applauded the developments as a long-awaited sign that their party was fighting back against the Republican wave created by November’s midterm election.

“I am glad to see some Democrats, for a change, with a backbone. I’m really proud to hear that they did that,” said Democratic state Sen. Judy Eason-McIntyre of Oklahoma, another state where Republicans won the governorship in November and also control both legislative chambers.

The proposal 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.

In addition to eliminating collective-bargaining rights, 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 the $3.6 billion budget shortfall.

Shawn Johnson of Wisconsin Public Radio contributed to this report, which includes material from The Associated Press. Copyright 2011 National Public Radio. To see more, visit http://www.npr.org/.