Give the Senate Republicans credit: They had to overcome remarkable hurdles to get their tax bill passed.

Approved of by just a third of the electorate, it was a poisonous bit of legislation, slightly more unpopular than even the 1993 tax hike under President Bill Clinton. The Senate had to pass the bill through reconciliation because no Democrat would sign up for massive tax cuts for the wealthy. This meant the GOP had to patch together an enormous pile of tax code changes, deals, and implicit tax hikes to both satisfy budget procedural rules and keep 50 Republican senators on board. They tried this gambit once before with TrumpCare and failed. It was a colossal political challenge.

Yet, when it came down to it in the wee hours of Saturday morning, the tax package squeaked through the Senate 51-49, with Sen. Bob Corker (R-Tenn.) the only GOP dissenter.

The Senate Republicans pulled this off through a singular focus on one overarching goal: The billionaire donor class must receive its payout, at any cost.

For all the bill's complexity, its underlying math is relatively straightforward: "By 2027, people making $40,000 to $50,000 would pay a combined $5.3 billion more in taxes, while the group earning $1 million or more would get a $5.8 billion cut," The New York Times reported, summing up analyses by the Congressional Budget Office and the Joint Committee on Taxation (JCT). It's an almost perfect one-to-one transfer of money from the vast numbers of Americans in the middle class to the far smaller population that occupies the upper fraction of the top 1 percent.

Indeed, for many families in the $40,000 to $100,000 range, the tax hikes will start as soon as next year.

No one needs to point to any second-order knock-off effects like interest rates or future debt burdens to explain how the GOP's tax plan fleeces ordinary Americans to line the pockets of millionaires. It's right there in the tax changes.

The cover story the GOP kept providing was that the tax cuts would trickle down into more jobs and higher wages for everyone. And you can certainly pick apart the economic mechanics of that claim. But you could also just listen to the people who actually run businesses in this country. When a roomful of CEOs was asked if they'd plow the money from the corporate tax cut back into new investments, almost none raised their hands. Bloomberg later reported that CEOs of major companies across the country were planning to pump the tax cut money into bigger shareholder payouts instead of jobs or wages.

It's not clear if the Republicans are just cynics who knew their fig leaf was just a fig leaf all along, or if their devotion to the trickle-down theory is so total that no contrary evidence could dissuade them of its power. Either way, none of this news slowed down the drive for the tax plan in the slightest.

Of course, the Senate version of the bill must still be harmonized with the House version before President Trump can sign it. But the two bills are similar enough that the House may just approve the Senate bill, rather than risk scaring off any marginal "yes" votes in the higher chamber. And Republicans really do seem deathly frightened of anything happening to their beloved tax cuts.

The reason why is no secret. Back in September, the Times reported that big-money donors were "furious" with the Republicans' failure to advance their agenda. This was in the context of the TrumpCare vote, but it was also obvious that tax reform was really the central focus. When asked in November what happens if that tax "reform" doesn't pass, Sen. Lindsey Graham (R-S.C.) told a reporter, "The party fractures, most incumbents in 2018 will get a severe primary challenge, a lot of them will probably lose, the base will fracture, the financial contributions will stop." When your overlords have made their will clear, you don't risk angering them by quibbling over details.

But the Republicans will almost certainly come to regret their rush to pass this toxic legislation. They have basically handed their Democratic opponents large in-kind donations in the 2018 and 2020 elections; by the time those judgment days roll around, plenty of non-wealthy Americans will be feeling the pain of this legislation.

The GOP has also completely sacrificed all credibility on "fiscal responsibility." Supposed deficit hawks barely blinked when the JCT released a dynamic score — accounting for the growth effects of tax cuts — that still found roughly $1 trillion in new debt over 10 years. It also turns out the Treasury Department won't bother releasing rival numbers. (Treasury Secretary Steven Mnuchin appears to have simply lied when he said his department would do so, which has kicked off an internal investigation.) That's an open door for Democrats to propose massive new programs and public investments, without feeling any need to explain how they'll be paid for.

More fundamentally, the tax bill reveals a Republican Party that is profoundly weak, despite controlling every branch of government. This legislation is a heist, pure and simple: a massive raid on the American people, done with speed and in the dead of night. That's not the act of a party confident in its hold on power. It's the act of a party desperate for one last big score.