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Senate Republicans started the clock for a final vote on their tax plan Wednesday evening, but among the unresolved demands from GOP waverers is a provision to prevent the bill from adding up to $1.5 trillion to the federal deficit over 10 years. No serious analysis has suggested the growth from slashing taxes for corporations and other businesses would make up that shortfall, and Republicans haven't offered any evidence. At a Politico Playbook forum on Wednesday, Sen. Marco Rubio (R-Fla.) said that cutting taxes needs to be followed by cutting spending on popular federal programs.

"I analyze this very differently than most," Rubio said. "Many argue that you can't cut taxes because it will drive up the deficit. But we have to do two things. We have to generate economic growth which generates revenue, while reducing spending. That will mean instituting structural changes to Social Security and Medicare for the future." He suggested reducing benefits and raising the retirement age for future retirees, so people can prepare for the changes. "Tax reform is the economic component of this equation," Rubio said. "When more people are working, there are more taxpayers and more revenue, but that alone won't be enough. You are still going to have a debt problem in the absence of spending cuts."

The broadly unpopular tax bill — rushed through with almost no debate or expert testimony and zero Democratic input — would have wide-ranging and uncertain effects on all Americans. As AARP noted, the legislation already includes $25 billion in automatic Medicare cuts for next year alone, along with $111 billion in other cuts to federal programs, and it would either raise taxes or keep them the same for 6.3 million Americans 65 or older in 2019 and 10.8 million by 2027. President Trump, who is pushing the legislation hard, promised during the campaign he would not change Medicare, Medicaid, or Social Security. You can watch Rubio's interview at Politico.