The Republican tax plan provides corporations with large permanent tax cuts. The plan also provides temporary tax cuts to the middle class that disappear over a ten year period. The middle class tax cuts have to be temporary so that the Republican Senate can pass the plan without any votes from Democrats. Senate rules allow the tax plan to pass with a simple majority as long as the plan does not increase the federal debt by by more than $1.5 trillion over a ten year period. They only need 50 votes from the 52 Republican senators to get a simple majority since the Vice President can cast a vote to provide a 51 vote majority.
Some senate Republicans have issues with the tax plan. Some are deficit hawks who object to any increase in the national debt. Others would like to make a few other changes to please their constituents. There is a lot of pressure on Republicans to pass any tax plan prior to the mid-term elections in order to demonstrate their ability to govern. However, the plan is not very popular with many voters who view the plan as a gift to corporations. Democrats should have an easy time making that point in the mid-term elections. The economics profession has many issues with the plan that raise important questions about GOP efforts to sell it as a plan for the middle class. The odds are that some kind of bad plan will get passed. We will have to see whether Democrats have the ability to convince voters that they cannot trust the GOP to look after their interests.