If the Republicans skewed the tax cut heavily towards the middle class, away from the ultra-mega-rich, the Dems would have no choice but to support it. And whereas the rich sit on the money and/or divvy it up to share holders for them to sit on, the Middle Class actually spend and propel the economy.
The benefit of putting money into the pockets of the poor / middle class cannot be understated. So much so that economic models have been suggested of guaranteeing a 20k/per year minimum allowance by the state -- per person -- would vastly solve many issues of poverty (eliminating welfare) while simultaneously stimulating the economy. I'm not on board with this theory, yet, but it's an interesting outside-the-box viewpoint that is actually being tested by some countries.
Tax cuts for the rich have been tried repeatedly, and every time it's been tried it has failed. Even the so-called success of the Reagan tax cuts tripled the debt.
The Reverse Robbin Hood Bill (robbing from the poor to give to the rich) is going pass. It's going to add a trillion dollars to the debt, it's going to raise taxes on the Middle Class, increase the cost of healthcare, and any benefit to the Middle Class is short-lived and will expire.
Sounds like a sweetheart deal for Republican donors. Trump voters, who largely rely on government benefits, who are the largest beneficiaries of Obamacare, and who wanted a president who looked out for their interests... just got snookered.
Watch in the post-Trump era, when a Democrat gets elected, when the Republicans again begin to worry about the debt. Gotta tighten that government belt by reducing government benefits (e.g. Social Security).