HARRISBURG — Pressure on Gov. Tom Corbett grew Tuesday to accept the federal government’s offer to fund the lion’s share of a massive Medicaid expansion now that Pennsylvania is virtually surrounded by states that are getting in line, including states run by Corbett’s fellow Republican governors.

Democrats seized on New Jersey Gov. Chris Christie’s decision to embrace the Medicaid expansion as an opportunity to paint Corbett and Pennsylvania as increasingly isolated from a growing group of states that will accept billions of federal health care dollars to help hospitals and doctors care for millions of uninsured people.

With Christie’s decision Tuesday, all of Pennsylvania’s neighbors are on board with the Medicaid expansion under President Barack Obama’s signature health care law, except for West Virginia, where Democratic Gov. Earl Ray Tomblin is still deciding.

“Pennsylvania is now essentially surrounded,” state Sen. Vincent Hughes, D-Philadelphia, told reporters on a conference call. “We are a deserted island in the health care oasis. ... We’re standing out here by ourselves.”

Corbett’s insurance commissioner last week called Medicaid a “broken” system and Corbett did not sway from his public stance Tuesday.

“The governor remains concerned about the cost of expanding Medicaid in Pennsylvania without reform,” spokeswoman Christine Cronkright said Tuesday.

The Corbett administration estimates Pennsylvania’s taxpayers will have to shoulder a $4 billion tab under the federal health care law over the next eight years. But that estimate includes costs that would occur anyway under the law and is much higher than an estimate from the Kaiser Commission on Medicaid and the Uninsured.

In addition, some governors calculated the tax benefit that would result from billions of federal health care dollars pumping into their state’s economy. Corbett did not. Meanwhile, Democratic lawmakers maintain the expansion would be a net tax benefit for Pennsylvania because federal money would relieve some of the state’s existing health care costs.

Senate Majority Leader Dominic Pileggi, R-Delaware, said Tuesday that his fellow Republicans in the GOP-controlled Legislature and members of the Corbett administration are becoming better educated on the issues involved with the Medicaid expansion by the day, and he echoed a Corbett administration complaint that information from the federal government has been lacking.

Republicans in the Senate are very concerned about the long-term cost of an expansion, but they are also hearing from hospitals about what a Medicaid expansion would mean to them financially and the consequences of a failure to expand, Pileggi said.

Pileggi also acknowledged Christie’s decision.