The Senate health care bill is expected to allow states to relax the Affordable Care Act rules only on benefits, not on pricing as the House bill does. But that change could impact people far beyond those states, according to a new analysis by the liberal Center for American Progress — because it could lead to a return of annual and lifetime benefit limits, and not just in the states with the waivers.

The bottom line: As many as 27 million Americans could face annual limits on their coverage, and 20 million could be hit with lifetime limits, according to the analysis.

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Expand chart Data: CAP analysis, 2015 American Community Survey, Centers for Medicare & Medicaid Services, 2017 Willis Towers Watson Survey; Table: Andrew Witherspoon / Axios

Why it could happen: The Affordable Care Act bans lifetime and annual limits, but only for the 10 categories of "essential health benefits" defined in the law. If a state decides that, say, prescription drugs or maternity care aren't essential benefits anymore, insurers can bring back annual and lifetime limits for them.

Why it could spread beyond those states: Large employers that operate in several states can choose which state they want to use as the basis for their benefits. So if an employer operates in 15 states, and one of them has a waiver from ACA benefit rules, it can set all of its benefits based on that state.

How the study was done: CAP based its estimates on a Willis Towers Watson survey of large employers, in which 20 percent said they'd bring back annual limits and 15 percent said they'd bring back lifetime limits if the ACA rules were repealed. It also used survey data suggesting how many people get their health insurance from large employers.