President Trump and Sen. Roy Blunt (R-Mo.). (Shawn Thew/EPA-EFE)

Looks like another week of debacles for the nation’s amateur president and the GOP leaders whose bus he hijacked last year.

Bid No. 3 to repeal and replace Obamacare has gone gurgling down the Senate drain. Alabama Republicans are headed to the polls apparently intent on choosing a notorious scofflaw over President Trump’s preferred candidate for a U.S. Senate seat. Trump’s incendiary attack on the free-speech rights of professional athletes has Americans in an uproar, while his reckless tweets about North Korea might be speeding us toward war. And in a pointless bit of cruelty, the bankruptcy-prone businessman delivered a scolding to hurricane-ravaged Puerto Rico — where entire towns are running out of food and water and the power may be out until 2018 — concerning the importance of repaying its debts.

Yet the stock market sails on.

The animal spirits of Wall Street are gliding through the craziness as blithe as Percy Shelley’s skylark. And the wind beneath the market’s wings is simply this: the promise of tax reform. Investors believe that America’s comparatively high corporate tax rate is a drag on economic growth, and they trust Congress and the president to deliver an invigorating cut.

But time is running out. At a recent meeting at the White House, Sen. Roy Blunt (R-Mo.) lived up to his name by telling Trump and Treasury Secretary Steven Mnuchin that tough decisions must be made right away. Details of a tax bill are naturally contentious, and they can only afford so many battles. “You need to quickly choose which of these fights you can win within 75 days,” he counseled.

Blunt is worth heeding on nuts-and-bolts matters such as this, because he is among the best vote counters ever to ride into Washington. The former history teacher served as majority whip in the House before his election to the Senate in 2010. Now, as vice chairman of the Republican conference, he continues to be a sensitive barometer of the ever-shifting political climate on Capitol Hill.

As he told the president, Blunt believes tax reform is a must-do before the December break. Failure to get it done by then would send the GOP into an election year with little to show for the luxury of one-party rule. To meet that rapidly dwindling timetable, the tax bill can’t be all things to all people.

Blunt’s own idea of a doable deal homes in on two targeted cuts. The first would land in the pockets of working people, while the other would deliver the GOP’s long-promised corporate relief. “Not everyone in my party understands this, but working people pay a lot of taxes even if they’re not paying income tax,” Blunt told me. A refundable credit for working-class parents could give millions of people the first real boost to their wallets in years, he said.

“If you’ve been in a stagnant income situation for the past 10 years, to suddenly have an additional $800 or $1,000 is meaningful. It might not sound like much money in Washington, but for a lot of people it can be a chance to do something fun as a family for a change, or maybe to eat out once a month at Applebee’s.”

Perhaps a working-class tax cut would help win popular support for a bill that also delivers for corporations. But that is hardly certain. A recent Wall Street Journal-NBC News poll found only 16 percent in support of lower corporate rates. Of course, that number might rise if more people understood that the sky-high stock market is counting on that cut, and that a disappointed market could derail the economy at just the moment when wage growth may be flickering back to life.

Before the Republicans can think about selling a tax bill to the voters, they need to settle on one among themselves. And so far, that isn’t happening. Quite the opposite: Lawmakers are squabbling like grade-school siblings sharing a back seat. Some senators, obsessed with the white whale of health care, want to tie their doomed quest to the hunt for a tax deal. Others are determined to reduce the top rate for high earners. Still others in the GOP caucus demand spending cuts to offset each tax cut, and everyone knows how difficult it is to cut spending.

In an ideal world, such important policies would not be decided on a party-line vote. But these are parlous times for bipartisanship. Democrats have shown by their solid stand on health care that they won’t do for Republicans what the GOP can’t do for itself. At best, a few endangered Senate Democrats might vote for a tax bill — but only after they see that Republicans have the votes for passage without them.

“Winning here is pretty important,” Blunt summed up, “for the party and for the economy.” And how, Mr. President, does tweeting about football players help achieve that victory?

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