Another Republican senator is sending a massive warning signal on Trump's tax plan

Republican Sen. Todd Young of Indiana expressed misgivings about the massive tax reform plan from President Donald Trump and GOP leaders, casting more doubts on the Republican framework in its initial stages.

In an interview with the Indianapolis Business Journal, Young suggested he would not support any tax plan that added significantly to the federal deficit. He said he would not vote for any legislation that would "blow a hole in the budget."

The senator said he would factor in increased economic growth due to the tax cuts when evaluating the impact of the final bill. Young did say, however, that he wouldn't assume "unreasonable rates" of growth.

"We need to recognize there are growth effects of improving our tax environment. Otherwise, what's the point of this process?" Young said. "But we can't assume unreasonable rates of economic growth or we're being fiscally irresponsible."

So-called dynamic scoring assumes that tax cuts would increase economic activity, raising incomes and profits. The increased profits would then be taxed, increasing overall tax revenues the government takes in.

The Trump administration projects in their score of the tax plan's outline that the cuts would lead to sustained 3% GDP growth, which would increase tax revenues and, they say, allow the plan to be deficit neutral. Most economists have cast doubt on the White House's assumptions.

Young told the IBJ he would take multiple economists' perspective into consideration when deciding whether to support the final plan, but cautioned that the framework was missing a number of key details.

Young's hesitations reflect those from Tennessee Sen. Bob Corker, who said last week he would not vote for a plan that "added one penny to the deficit," but would also evaluate the plan's potential effects on economic growth.

Young's comments are concerning for GOP leaders, since the party only holds 52 seats in the Senate. Party leaders plan to use the process known as budget reconciliation, which would allow the eventual final tax bill bypass a Democratic filibuster and pass with a simply majority.

So far Corker, Young, and Sen. Rand Paul of Kentucky have all expressed misgivings about the tax framework.