The way to defeat poverty in America, Republican Sen. Marco Rubio says, is to let the states lead the fight. Here's how to tell if he's serious about that.

Rubio's basic premise, that the federal government has been inefficient at the job, is sound: Despite the impressive success of the anti-poverty programs created 50 years ago -- including food stamps, greater Social Security benefits and federal subsidies for poorer school districts -- the United States still has almost 50 million people living in poverty. The U.S. spends more per resident on social programs than the average for developed countries, but gets worse results.

The senator's proposed solution -- replacing federal anti-poverty programs with block grants for states to use as they see fit -- has a certain appeal, too. As Rubio, of Florida, puts it, why should we assume that what works in Tallahassee makes sense for Topeka?

But there are practical reasons to be wary of giving states unconstrained control over federal anti-poverty money. Few states can match the federal government's resources to plan, monitor and analyze programs, including investigating their abuse. And if the U.S. government surrenders all control over that money, it's hard for it to remain accountable to taxpayers for how the dollars are spent.

A more fundamental rejoinder to Rubio's plan is that the nature and causes of poverty don't vary from state to state nearly as much as the political will to alleviate it does. The best illustration of this is the expansion of Medicaid under the Affordable Care Act: Only half the states have agreed to take new federal money to provide Medicaid for more people. That level of disregard for the vulnerable doesn't bode well for letting states control more such programs.

Obamacare also contains a remedy for this problem, however. The health-care law gives states the chance to disregard its major provisions, including the individual and employer mandates and the new standards for what insurance must cover, while still collecting the same federal money they would get otherwise.

To qualify, a state needs to come up with an alternative program that meets the same basic objectives as the law: Cover the same number of people, with the same quality of insurance, at the same cost or lower than Obamacare. The same approach applied more broadly would give states the flexibility that Rubio calls for, while guarding against the risk that the people who need help will be left worse off.

As it stands, Rubio's proposal for blanket state autonomy looks less like a recipe for reducing poverty than a way to abdicate federal responsibility. If the senator is right that state leaders can do a better job of designing effective anti-poverty programs, he should give them a chance to prove it.

Bloomberg News.