By reducing the amount the federal government collects in taxes each year — at a time when federal tax collections are already a smaller share of the economy than they have been in more than half a century — the Republican tax plans will make it harder to balance the budget, said Robert L. Bixby, the executive director of the Concord Coalition, a nonprofit group that advocates fiscal responsibility.

“If the first thing you do is lower revenues by that much by extending all of those tax cuts, then you have a much bigger hole to dig out of to get back to a balanced budget,” he said in an interview. “The hole they’re digging, to mix metaphors, is a self-inflicted wound.”