A business tax cut Oregon Gov. Kate Brown hopes to speed through the legislature in May could be smaller than first anticipated, a new analysis suggests. But in the context of the special session Brown plans to call on May 21, that might be a relatively slight curveball.

As legislative leaders on both sides of the aisle preach the need for a session narrowly focused on tax cuts for a small subset of businesses, there are signs other lawmakers have different ideas. Rumors are rife about a range of policy proposals — from gun control to greater tax breaks — that could come to the surface when Brown summons legislators back into action.

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“There are individual members who can do what they want and break ranks in an election cycle," said state Sen. Brian Boquist, R-Dallas, the vice-chair of the Finance and Revenue Committee. "It could be interesting."

Already, the picture is shifting around the one item legislators are guaranteed to take up in the session: extending favorable tax rates to small businesses known as "sole proprietorships."

Last week, the state's Legislative Revenue Office (LRO) estimated that a tax break Brown has in mind would slash taxes by between $11.5 million and $13.3 million in years to come. That's a smaller blow to state coffers than was expected in an earlier $15 million per year estimate from the Department of Revenue.

Related: Oregon Governor Calls For May 21 Special Session On Business Tax

But the LRO's analysis differs in another meaningful way: It estimates that some 12,000 businesses will be eligible for the tax break Brown's floating—a jump up from the 9,000 businesses contemplated in the earlier analysis. The new estimate expects about 4.3 percent of Oregon's sole proprietors will benefit from lower taxes.

The differences between the analyses are relatively small, but that doesn't mean they won't matter. Republican lawmakers are still upset the governor signed a bill in April that blocked a tax cut for a larger segment of businesses, and have called her subsequent push for a tax cut election-year theater.

"The political theater session now has a date," House Minority Leader Mike McLane, R-Powell Butte, said in a statement after Brown announced the May 21 session last week. "Let's hope Governor Brown and legislative Democrats will limit the scope of the session to the stated purpose instead of allowing for the introduction of unrelated policy bills."

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Leading Democrats have publicly vowed to limit the scope of the special session to the tax tweak. Boquist says a deal has not been struck.

“The governor wants to keep it to one topic and one topic only and that’s the small business piece; problem is, she’s not a member of the Legislature," Boquist said.

Boquist —who said he believes Brown’s tax break could be addressed during a regular session and that the special session is unnecessary—said Republicans are floating the idea of expanding her proposal to add a deduction for student loans or increase the deduction for low-income individuals.

There has also been some talk from Democrats about clarifying Oregon laws to give retailers the ability to raise the minimum age for buying a firearm without fear of being sued.

Following the shooting at a Parkland, Florida, high school in February, Dick’s Sporting Goods and Walmart raised the age for buying a firearm at their stores to 21 from 18. An Oregon man immediately sued the stores for age discrimination.

Lawmakers could add an exemption to the state’s discrimination law to include the age of firearm sales, similar to current exemptions for alcohol and marijuana sales.

The tax bill Brown says she'll propose would extend a tax rate as low as 7 percent to income from sole-proprietorships, whose owners pay business taxes as part of their personal tax returns. They're currently taxed at 9 or 9.9 percent.

In order to qualify under the current proposal, sole proprietorships need to have at least one employee who isn't the owner.

The governor's office has painted the cut as righting an overdue injustice. The Legislature extended the same tax break to many other businesses in 2013.

“I’m simply not willing to let these main street businesses … go through another tax year with unfair tax treatment as compared to their larger competitors,” Brown said last week.

Much of the benefit of Brown's bill would go to the most successful businesses. More than 40 percent of the relief would go to sole proprietorships with $500,000 or more in annual income. Nearly three-quarters of the tax relief would be felt by businesses with at least $200,000 per year in income.