Why turn down free money? Democrats and the Obama administration say that states who don't accept funding for Medicaid expansion are making a political point, but those on the ground in the states say there is more to it.

President Barack Obama's signature health care law has long been a lightning rod, and his party argues that opposition to "Obamacare" is partisan politics that leaves America's poorest and most vulnerable without coverage. White House Press Secretary Josh Earnest said earlier this year that some Republicans were "quite literally putting their political ambition against the lives of some people."

Of the 20 states that have refused to expand Medicaid, 17 are led by Republican governors and 18 have legislatures controlled by Republicans.

But while some Republicans in Congress might be scoring political points with voters by passing bills that aim to repeal the Affordable Care Act, those running state governments say they have a more practical decision to make: Expand Medicaid and receive federal assistance that will decline over five years, or refuse to expand and be accused of playing politics with health care for the poor.

States are faced with tough fiscal choices each year as they strive to balance their budgets. Medicaid already takes up the largest share of most state budgets, and its costs grow much faster than revenue.

"Everything has taken a backseat to the Medicaid budget," says Maine Rep. Deborah Sanderson, Republican ranking minority member of the state's health and human services committee. "We feel it every session."

Maine Gov. Paul LePage, a Republican, has vetoed Medicaid expansion three times during the 126th legislature, and it remains the only state in the Northeastern part of the U.S. that hasn't taken part.

Over the years states have sacrificed other portions of the budget, including transportation and infrastructure, to pay for Medicaid. It doesn't help that health care is growing faster than the rest of the economy, nor that the cost of prescription drugs has heaped demands on the program. Further, government analysts say Medicaid is one of the main causes for the growth in the rate of health care spending.

"We can't go in the hole," says Georgia state Sen. Renee Unterman, Republican chairwoman for the health and human services committee. "We can't borrow this year thinking the economy will balance next year. … That money looks enticing but you have to dig deeper."

While the federal government has vowed to fully cover the cost of expansion until 2016, states gradually would be responsible for more and more, until they have to carry 10 percent of the cost by 2020.

Some lawmakers have said they don't trust that the federal government will honor its commitment to keep up this level of support over the long term, and others say that even paying 10 percent of the cost is too much for their already-strained budgets. "Ten percent of $5 billion is a lot of money," says Sanderson.

Maine pegs the cost of expansion at $125 million a year. Other non-expansion states have their own estimates. Georgia's state budget office puts the cost at $2.5 billion over a decade. Nebraska estimates increases from $4.4 million in 2017 to $26.6 million by 2020, and Alabama projects its costs would reach $710 million over the next six years.

Originally, the Affordable Care Act was written to expand Medicaid coverage to nearly 17 million Americans with incomes up to 138 percent of the federal poverty level, or those earning less than $16,243 for an individual and $33,465 for a family of four in 2015. But in 2012 the Supreme Court ruled that states could decide for themselves whether they wanted to participate in expansion.

States can expand at any time, and so far 30 states and the District of Columbia have opted to do so.

In states that haven't expanded Medicaid, millions are left without health insurance. They don't make enough money to obtain tax-subsidized insurance that are also provided under Obamacare through government marketplaces, but they earn too much to qualify for Medicaid in their state.

North Carolina is another state that has not expanded. "It's not political, though some are trying to make it political," says state Sen. Louis Pate, Republican co-chairman of the state's health care committee.

He explains that during the first four years that Republicans had control of the state's legislature they had to make up a $2.5 billion budget deficit in part attributable to cost overrides in Medicaid. "It's a system that's just out of control in our state," he says. "It has kept us from being able to give teachers raises and has taken away from our roads and justice system. That really hurts our state and it hurts our population."

Proponents of expansion argue the state estimates don't include potential savings that could result by lowering the costs of caring for uninsured patients and keeping people healthier and out of the hospital.

In Maine, Sanderson says the state already had experience with expanding Medicaid to cover more people in the late 1990s and early 2000s. Twice the number of people signed up for Medicaid as had been projected, and the program's share of the state budget went from 13 percent to its current 25 percent. Sanderson says proponents of expansion promised lower emergency room usage and less charity care from hospitals, but she says these savings weren't realized.

Some states that expanded Medicaid did so through working with the federal government to create Medicaid waiver programs, in which they are given special approval by the U.S. Department of Health and Human Services to experiment with alternatives to traditional Medicaid. Six of the states that have expanded have done so this way.

Montana recently expanded its Medicaid program after federal health officials approved a requirement that beneficiaries pay premiums that amount to 2 percent of their income.

Other states long opposed to expansion may soon reverse course as well.

Former Louisiana Gov. Bobby Jindal often touted his record of refusing to expand Medicaid in the state when he was running for the GOP nomination. But the state's Democratic governor-elect, John Bel Edwards, says expanding Medicaid will be one of his highest priorities when he gets into office in 2016.