Nevada Sen. Dean Heller said Friday that he planned to vote &nbsp;against the Republican healthcare bill, a potentially key defection.Although the White House and Majority Leader Sen. Mitch McConnell of Kentucky have said they plan further negotiations over the bill,&nbsp;"it's going to be very difficult to get me to a yes," Heller said at a news conference in Nevada with Gov. Brian Sandoval (R).The bill unveiled Thursday by McConnell is "simply not the answer,&rdquo; he said. "In this form, I will not support it."Given the unified Democratic opposition to the bill, McConnell can afford to lose only two Senate Republicans, so Heller's announcement is significant.A no vote by Heller would not seal the fate of the bill, however. Heller is widely viewed as the most vulnerable Republican senator up for reelection in 2018 -- the only one running in a state that Hillary Clinton carried last year -- and Republican leaders have been hoping to avoid having to count on his vote.Heller cited several reasons for opposing the bill, but the chief one was its deep reductions in federal support for Medicaid."This bill will mean a loss of coverage for millions of Americans and many Nevadans," he said.Nevada, under Sandoval, has used its authority under the Affordable Care Act to expand Medicaid, which has given health coverage to more than 210,000 additional state residents, Sandoval said."These are folks who are worth fighting for," he added.The cutbacks the Senate bill, which would end Medicaid expansion, would cost the state $120 million a year by 2022, with the cost rising sharply after that the governor said. "That's a cost that the state cannot sustain."Heller also cited the bill's impact on treatment for opioid addiction and the likelihood that the plan would fail to reduce premiums."There isn't anything in this piece of legislation that will lower your premiums," he said, contradicting one of the main arguments that supporters of the bill have made.Heller's announcement increases the pressure on McConnell to find ways of persuading several other reluctant senators to support the bill.Four conservatives, Sens. Rand Paul of Kentucky, Mike Lee of Utah, Ted Cruz of Texas and Ron Johnson of Wisconsin, said Thursday they were opposed to the bill in its current form because it does not go far enough to roll back the Affordable Care Act.Several more centrist senators, including Sens. Susan Collins of Maine, Lisa Murkowski of Alaska, Rob Portman of Ohio and Shelley Moore Capito of West Virginia, have voiced concerns similar to Heller's about the depth of the bill's Medicaid cutbacks and its impact on opioid&nbsp;treatment.Collins and Portman have both said they want to review the analysis of the bill from the Congressional Budget Office before making up their minds. The budget office has said it will release that assessment early next week.