Story highlights The Senate voted to start floor debate Wednesday on the GOP tax plan

It's unclear if Republicans have the votes for final passage

Washington (CNN) The Senate has passed a procedural vote on the tax bill that allows debate to begin on the measure with a final vote expected late Thursday or Friday.

The procedural vote passed 52-48.

As the vote was finishing, President Donald Trump said on Twitter, "This week, the Senate can join the House & take a strong stand for the Middle Class families who are the backbone of America. Together, we will give the American people a big, beautiful Christmas present-a massive tax cut that lets Americans keep more of their HARD-EARNED MONEY!"

After learning blistering lessons from their health care debacle , the GOP Senate has managed -- so far -- to hold their conference together and keep inching toward legislation that will extensively rewrite the country's tax code for the first time in three decades.

But, behind-the-scenes negotiations continue and there is plenty that could go wrong. The party nearly skidded off schedule Tuesday over concerns from Sens. Bob Corker of Tennessee and Ron Johnson of Wisconsin. Corker wanted to ensure that tax bill would actually lead to economic growth and was able to secure an agreement in principle that would trigger some kind of automatic tax increase if the GOP's anticipated growth didn't materialize. Johnson, meanwhile, went into the GOP tax vote in the Budget Committee still frustrated about the way the tax bill treated tax rates for pass-through business income, but voted anyway to advance the proposal, saying that he wanted to keep the process going.

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