Fearing the worst, aldermen and outside groups have begun laying down conditions ahead of Mayor Lori Lightfoot’s State of the City address Thursday evening, in which she is expected to present the scope of Chicago's budget challenges.

Lightfoot said earlier this week she would not get into “granular” detail in the speech. Aldermen said Wednesday they had not heard a specific shortfall number, but expected the budget hole to lie between $750 million and $1 billion. Progressive aldermen pledged proactively to “say no to regressive revenue measures” that hit working families’ pocketbooks.

The speech will encompass “what we walked into, what we’ve done, and what we see as the path forward,” the mayor said this week.

Former Mayor Rahm Emanuel's CFO, Carole Brown, previously attributed the huge projected deficit to a combination of factors, including the city’s move to quit borrowing funds that should come out of current spending, increased pension costs and poor returns on 2018’s pension investments.

Budget watchers say police overtime, legal settlements and expected costs for retroactive wages in new contracts will also play a large role in the deficit.

Emanuel faced a $635 million budget shortfall when he took office. He raised property taxes, water fees and the 911 surcharge to plug the structural deficit and put the city’s pensions “on a path to solvency.” While he shrunk the city’s structural gap, Lightfoot will still have to come up with a way to reach projected increases in pension contributions.

Ten of the city’s 50 aldermen—most new, all progressive—signed a letter urging Lightfoot to use the budget to build "a city that provides for the many, not just the wealthy few"—and tax the rich and businesses before raising property taxes across the board.

Aldermen mentioned bringing back the corporate head tax that Emanuel eliminated, instituting a corporate lease tax similar to New York City’s, or instituting the so-called LaSalle Street tax, which would hit financial transactions.

They pledged to negotiate and vote together as a bloc, with the potential to add ranks from the other eight members of the Progressive Caucus.

“We will not ask poor and working people to continue to carry the lion’s share of the burden in place of those who profit from their low wages, evictions and crumbling schools. We understand the seriousness of the projected budget shortfall, and we are prepared to dig in and work hard to find solutions. We need to work together to prioritize working people–not wealthy developers,” a letter from the group, aligned with the political organization United Working Families, said.

“It’s not just thinking about our bloc as something that’s going to get in the way of something, but why it’s important to have us on your side,” Ald. Maria Hadden, 49th, said. “We’re a bloc that’s still a significant number that can make or break a decision.”

Ald. Susan Sadlowski Garza, 10th, said both Lightfoot and Budget Chair Pat Dowell, 3rd, had been nothing but transparent, and she was hopeful for upcoming negotiations.

“This isn’t about Council Wars, it’s about working together to find the best solutions,” Garza said.

“She didn’t talk about any cuts, cuts never came out of her mouth,” Garza said about the mayor, adding Lightfoot’s focus in briefings was on savings. “They’re literally scouring every department, every budget to see where we can save money.”

Meanwhile, advocates for the homeless plan to rally before Lightfoot’s speech at Harold Washington Library, asking the mayor to stick to a campaign pledge to support a dedicated funding stream to address homelessness in Chicago.

The group wielded “broken promise” props at an event marking Lightfoot’s first 100 days in office on Wednesday morning.

“This week, the mayor said that her ‘commitment to doing something to address both of these issues (homelessness and housing instability) remains as firm as it was, from the day I took office, to now.’ But Mayor Lightfoot still does not say how she will do that, nor has she explained backpedaling on her commitment to dedicate a (real estate transfer tax) increase to homelessness and housing,” a news release from the Bring Chicago Home coalition says.

Lightfoot's address will be streamed online and live on TV and radio at 6 p.m. Thursday.