In a letter, Rep. Gerry Connolly (D-Va.) urged him to not to let the opportunity pass.
"The choice we face as Virginia’s leaders is momentous," he wrote. "Will we allow this once-in-a-lifetime opportunity to leverage billions of dollars of federal funds to help Virginia’s families, businesses, and bottom line?"
A statement from Connolly's office stated that Virginia stands to gain $17 in federal funds for every dollar it spends on Medicaid.
In his letter, Connolly also cited a McDonnell-sponsored health council that found that Affordable Care Act reforms would reduce the amount of care that goes uncompensated in Virginia.
"Opting out of the Medicaid expansion would cause uncompensated care costs to continue spiraling out of control," he wrote.
McDonnell called the Medicaid expansion "another long-term unfunded mandate, another major budget-busting burden" after the Supreme Court ruling.
He told reporters that GOP governors are focused on getting the party's presidential candidate, Mitt Romney, elected in November rather than implementing the healthcare law.