On Capitol Hill, the Senate could vote as early as today on a Republican tax plan that would shower billions of dollars in tax cuts on the richest Americans and corporations—but their effort hit a snafu when the nonpartisan Joint Committee on Taxation said the bill would add $1 trillion to federal budget deficits over the next decade. Its report directly contradicted claims made by Treasury Secretary Steven Mnuchin, who’s repeatedly claimed the tax cuts would pay for themselves by stimulating the economy. Mnuchin had promised to release a Treasury Department analysis backing his claims, but he has yet to release any data, and Treasury officials at the Office of Tax Policy told The New York Times they haven’t been tasked with researching the bill’s impacts. On Thursday, the tax plan got a major boost when Arizona Republican Senator John McCain said he’d vote in favor of the bill. Critics say the tax cuts could trigger billions of dollars in cuts to Medicare, including cutting off access to chemotherapy and other cancer treatments. Senator McCain’s support for the bill came a day after his doctors said they’d discovered a second tumor in his brain. Meanwhile, a little-known provision within the Republican tax bill would open one of the world’s last pristine wildernesses—the Arctic National Wildlife Refuge—to oil and fracked gas drilling. We’ll have more on that provision later in the broadcast.