Multiple outlets have confirmed that Senate Democrats in Wisconsin boarded a bus and left the state, denying the Republican majority the quorum needed to pass their budget repair bill, which strips away collective bargaining rights for public employees. Sen. Jon Erpenbach told WisPolitics that the Democrats were left with no choice:

Asked how long they were prepared to remain outside Wisconsin, the Middleton Dem demurred.

“The question is when are the Republicans going to sit down seriously with the other side on this issue and try to work something out,” Erpenbach said. “When are we going to be reasonable about this and slow things down?” [...]

Erpenbach said Republicans should look at how the proposed changes are tearing the state apart and realize a different path is needed.

“This isn’t anything that we do lightly at all. This isn’t a prank. This isn’t a joke. This is Democrats standing together saying slow down.”

This comes as protests continue to rage inside and outside the Capitol. The Department of Administration counts nine arrests so far, and as for crowd size, the same agency (conservatively) estimates 25,000 out in force, including 5,000 inside the Rotunda. Governor Scott Walker again threatened to call out the National Guard if the protests got “out of hand.” The Center for Media and Democracy’s PR Watch has live updates of the rally.

Wisconsin has become the critical start point for a much broader assault on worker’s rights and unions. Ohio has seen similar protests over a very similar bill. And states like Arizona, Florida, Indiana, Iowa, New Hampshire, New Jersey and New Mexico are considering additional limits on public employee rights, though not to the extent of Ohio and Wisconsin.

The origins, as I wrote about Monday, come from ALEC, the American Legislative Exchange Council, a key driver in the conservative movement. One reason why you see similar bills from Republicans pop up in multiple states is ALEC, which pushes an agenda for state legislators to pick up and run with. We know that ALEC brought together Walker and southern state Governors after the elections to discuss so-called “right-to-work” legislation. We know that ALEC commended Walker for his first successful piece of legislation, the bill slashing business taxes that created the budget deficit which he is now exploiting to take away public employee rights. They are basically behind all of this.

This fight could now play out over many weeks, depending on how long state Democrats – or the Governor – hold out. And I don’t think the working families rallying in Madison have any quit in them, either.

UPDATE: John Boehner has come out in favor of Gov. Walker in Wisconsin. Walker himself demanded that Democrats come back to work and allow the bill to move forward. Hosni doesn’t like it much when the people don’t obey his demands.

UPDATE II: A poll for Building a Stronger Wisconsin finds pretty sharp opposition to the union-busting bill:

One-third of those surveyed last night said they backed Walker’s proposal to increase how much public employees pay for their health care and pensions.

Almost 27 percent said they believed public employees should pay more for their health care and retirement benefits, but Walker’s plan went too far. Another 35 percent said they opposed the proposal as “an attack on unions and Wisconsin workers.”

When told the proposal also included stripping public employees of their ability to collectively bargain on any issue other than wages, support for the proposal dropped slightly to just less than 32 percent.

Thirty-two percent said they supported the increased employee contributions, but thought the collective bargaining piece went too far. Thirty-three percent opposed it as an attack on unions and workers.

UPDATE III: State Sen. Chris Larson talked to Greg Sargent and basically said the Democrats won’t come back until this assault on workers ends.

“Each of us is in a secure location,” he told me, confirming that they were not all together but were monitoring events on the Web and on Twitter. Larson refused to say whether he and his fellow Dems had left the state, as some have speculated.

“We’re going to be staying away until we hear that they are taking the right to organize seriously,” Larson continued, referring to Republicans. “They’re going after 50 years of history in one week. Until they take that off the table, it’s a non-starter.”