Here’s why the GOP is coming up short on votes to repeal Obamacare

Voters cast their ballots at the polling place at Fairfax Circle Baptist Church during Super Tuesday voting March 1, 2016 in Fairfax, United States.
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For the last seven years, House Republicans have voted dozens of times to repeal or roll back provisions of the Obama administration's signature health-care law.

Now, with control of all three branches of government, the GOP appears to be coming up short on a bill to repeal and replace key portions of the law.

Despite a fierce lobbying campaign by the White House, House Republicans Wednesday had not lined up enough votes to secure passage of the American Health Care Act, which was expected to come up for a floor vote sometime Thursday.

Some GOP holdouts have said the bill doesn't go far enough to provide affordable coverage; others have said it goes too far and costs too much.

Republicans need just 215 votes – shy of the full 218-vote majority – because of several seats left vacant by the nomination of Trump Cabinet appointments. But the latest "whip count" shows that more than two dozen GOP House members plan to vote "Nay" on the bill, according to a tally compiled by NBC News.

To better understand why, CNBC took a closer look at the district-by-district politics of the first major legislative initiative of the party in power.

With an eye on the 2018 election, many GOP House members can safely "vote their conscience" with little fear of alienating voters back home. In the last election, some 85 GOP members ran unopposed or won more than two-thirds of the votes cast. (More than 100 House Democrats enjoyed the same comfortable victories.)

But more than two dozen GOP House members were elected from districts that have a markedly blue tint; 12 of those districts voted for Democratic presidential candidates in the last three elections. Democrats won the top of the ticket at least once in the last three elections in another 48 districts now held by House Republicans.

Despite the GOP's persistent attacks on Obamacare, the law proved popular with voters in many congressional districts, according to the latest data available. By using county-level enrollment tallies, researchers at the Kaiser Family Foundation developed estimates of how many voters had signed up for health insurance under the law. (The data are as of the end of March 2016 and do not include millions more voters who signed up for expanded Medicaid coverage.)

The data show that in 17 GOP-controlled congressional districts, the number of voters who signed up for Obamacare coverage was equal to or greater than the vote margin of victory for that House member.

In other words, if the GOP plan forces some of those voters to go without health insurance, that margin of victory will be eroded in 2018.

The GOP bill would also shift health-care costs to the states and has many governors worried that the plan would create a financial squeeze on their budgets.

The joint state-federal Medicaid program for low-income households grew rapidly under the 7-year-old Affordable Care Act (ACA), better known as Obamacare, and has been consuming a larger share of many state budgets every year.

States currently run the Medicaid program and pay part of the cost; Washington pays the rest based on a formula that varies from state to state, no matter how much the program costs. The new proposal would replace those reimbursements with a fixed payment.

That would leave the states on the hook for extended coverage or rising costs beyond those capped federal contributions. The change would create a greater financial burden on states, Moody's reported.

The Congressional Budget Office has estimated that the block grant systems could cut Medicaid spending by as much as a third over the next decade.

Under the ACA, states were offered the chance in 2014 to expand eligibility to more people. Thirty-one states and Washington, D.C., took advantage of the offer and added 15.7 million people to the program, according to government data. That expanded Medicaid rolls to about 73 million people, about half of whom are children.

State Medicaid spending has been growing steadily, placing a financial strain on state budgets and forcing tax hikes or spending cuts to make up the difference. The state share of Medicaid spending is expected to grow to 28 percent of tax revenue by 2025, up from 24.5 percent in 2017, Moody's estimated.

The new funding formula could also reduce or eliminate coverage for millions of people.

That impact of Medicaid expansion on individual state budgets varies widely. Alaska and North Dakota spend just 5 percent of their overall revenue on Medicaid spending. New York, Massachusetts, Missouri, Pennsylvania, and Rhode Island spend 20 percent or more.

Watch: Trump meets with health-care CEOs