Governors and legislatures in the 25 states not expanding Medicaid have cited what they believe will be added costs from covering more people under the program, which could require tax increases, and the fear the federal government will renege on its promises to pay the lion's share of costs for not expanding the program. However, many analysts said another motivation is adamant opposition to President Barack Obama and his signature health-care law, as well as the presidential aspirations of some Republican governors.
The tax impact related to Medicaid expansion issue will affect employers with more than 50 full-time workers who don't offer health insurance considered affordable as of 2015, when the mandate to provide such coverage begins.
If those health plans cost workers more than 9.5 percent of their family income, or if the health plans pay for less than 60 percent of their medical costs, employees can go to the government-run Obamacare exchanges such as HealthCare.gov to obtain health coverage. In states expanding Medicaid, people who earn less than 139 percent of the federal poverty line, about $15,000, can qualify for Medicaid coverage without their employer incurring a tax penalty for them.
But in states which are not expanding Medicaid, employees at such companies who earn between 100 percent and 139 percent of the federal poverty level—between $11,600 and $15,000—will be eligible for government subsidies to buy private Obamacare insurance from the exchanges.
If those workers use those subsidies to do so, their employers must pay a tax penalty of up to $3,000 per worker. The penalty is capped at $2,000 multiplied by the total number of full-time workers, minus 30.
(Read more: Wanted: Young Obamacare enrollees)
Haile said that when he's tried to explain the potential tax hit to employers, some of them assume the penalty is the same for them as the lowest fine for individuals who forgo health insurance this year: $95.
When he tells them the penalty for companies, they often yelp, Haile said: "'What do you mean, $3,000?'"
"You really get the attention of business folks," Haile said.
His analysis notes that for states not currently expanding Medicaid, "any projections of the 'net' costs of Medicaid expansion should also reflect the very real costs of the shared responsibility tax penalties to employers" in those states.
—By CNBC's Dan Mangan. Follow him on Twitter @_DanMangan.