Protesters in Wisconsin promise the biggest turnout yet in Wisconsin's capitol Thursday.

Union leaders say they expect tens of thousands of workers to turn out in Madison, and around the state. State Democratic senators will not be among those there, however--the 14 state senators left Wisconsin last week to stop the passage of a bill that would strip public workers of their collective bargaining rights.

The mass exodus of the senators, who are holed up in an undisclosed location for safety reasons, is preventing the Senate from taking up the measure, because at least one of the 14 Democrats is needed for a quorum.

The "Wisconsin 14," as they have dubbed themselves, are staying away despite threats against them. The state Senate has passed a rule that they must appear in person to get their paychecks.

Wisconsin Gov. Scott Walker is holding firm with his position, stating Wednesday that public workers must make concessions during the state's budget crisis. He says he has the votes to approve the bill--which can't advance as long as the "Wisconsin 14" stay out of the state. The Wisconsin Assembly took up the bill Tuesday, but Assembly Democrats used a filibuster to successfully block the vote.

The bill would require most workers in the public sector to contribute more to their pensions and health insurance, as well as strip unions of collective bargaining rights on anything other than salaries.