McLean, VA (written by Richard Wolf/USA Today) -- The Supreme Court's decision upholding President Obama's health care law but potentially limiting its scope has created a stark political divide among the nation's governors.

A 50-state survey by USA TODAY shows only Republican governors are refusing to expand Medicaid and only Democrats are vowing to expand it following the court's ruling that states cannot be penalized for failing to enlarge the program. More than half the governors are undecided.

The partisan gulf exposes problems for the law as it staggers from the 5-4 court decision, past GOP efforts to repeal it in Congress and toward a November election that could decide its fate. Without broad action by states, millions more Americans will remain uninsured, hospitals will face continuing demands for uncompensated care, and insurers may be forced to raise premiums.

"The low-income uninsured will continue to place financial pressure on the health care delivery system," says Diane Rowland, executive vice president of the non-partisan Kaiser Family Foundation.

The survey found seven Republican governors refusing to expand Medicaid and 22 others in doubt. Together, they represent nearly 10 million people who were projected to join the program.

"While we absolutely need to address the challenges of the uninsured, expanding Medicaid may not be the way to do it," says Utah Gov. Gary Herbert, a Republican. "Let's start this conversation over. . . with the states at the table."

By contrast, 13 Democratic governors and independent Lincoln Chafee of Rhode Island are fully implementing the law. Seven Democrats have not committed to expand Medicaid.

About 16 million people were projected to gain Medicaid coverage under the law, 60% of whom live in states with Republican governors. The court ruling threw out threatened federal penalties against states that do not comply, freeing states to reconsider the expansion.

Most Republican governors and legislatures also are on the fence or have decided not to set up state health insurance exchanges where individuals and small businesses can shop for plans. Just four are moving forward with such exchanges; the other states face delays or inclusion in a federal exchange.

Several of the nation's largest Republican-run states, such as Texas and Florida, previously announced their intent to sidestep the law. Texas Gov. Rick Perry on Monday called it a Washington "power grab." On Tuesday, the Republican Governors Association (RGA) wrote President Obama with a list of 30 outstanding questions. On Wednesday, Nebraska Gov. Dave Heineman, chairman of the National Governors Association, said his state can't afford the Medicaid expansion.

"Medicaid has been on an unsustainable path, comprising a growing share of state budgets every year," wrote Virginia Gov. Robert McDonnell, the RGA chairman. "It is difficult to see how expanding Medicaid without reform would do anything other than put more strain on state budgets and the taxpayers."

The Obama administration hopes most states fall into line. For three years, the federal government will pay to expand Medicaid to adults earning up to 138% of the federal poverty level - $31,809 for a family of four. States gradually will pick up 10% of the cost by 2020.

Currently, states are not required to cover childless adults. Still, "we think this is a deal that states, in the end, won't want to turn down," Secretary of Health and Human Services Kathleen Sebelius says.

The give-and-take between Republican governors and the Obama administration comes as the nation's governors hold their annual meeting this weekend in Williamsburg, Va., and four months before elections that will decide who controls the White House, Congress and 11 governors' offices.

The results of the federal election could sway states' decisions. If Mitt Romney leads Republicans to power, the health care law could be weakened or repealed, bolstering the position of GOP governors. If Obama is re-elected and Democrats retain control of the Senate, states may have reason to accept the Medicaid expansion, since all taxpayers will share in the cost.

In addition, newly elected governors and state legislators will have influence before the Medicaid expansions and insurance exchanges are scheduled to take effect in 2014.

Many states are backing away. "We struggle to fund our Medicaid program in its current condition," says Mississippi Gov. Phil Bryant, a Republican. The state can't afford an expansion "that would put one out of every three Mississippians on the program."

Most Democratic governors plan to plow ahead on both the Medicaid expansion and the creation of insurance exchanges, from which millions of people will choose coverage plans. "If the expansion is going to be there from the federal government, I don't know how you can turn your back on a couple hundred thousand of your working people," says Arkansas Gov. Mike Beebe, a Democrat.

Democratic governors in Delaware, Kentucky, Missouri, Montana, New Hampshire, North Carolina and West Virginia remain undecided about their plans, however.

"Unlike the federal government, Montana can't just print money," says Democratic Gov. Brian Schweitzer, whose state faces $71 million in costs over 10 years. "A new approach to controlling health care costs is needed. There are still a lot of unanswered questions."