Donald Trump, master of the Senate. Photo: Shawn Thew-Pool/Getty Images

The Republican Party is trying to pass a big tax cut on an expedited basis, even though the full plan does not yet exist, and every time Republicans have come up with a specific policy to offset the $5 trillion revenue hole they need to fill, it gets shot down. (The most recent being a proposal to cap 401(k) contributions, which President Trump vowed yesterday to keep in place.)

In the midst of this highly ambitious agenda, which even the most skilled and focused administration would be hard-pressed to carry out on time, Trump is … raising beefs with two Republican senators whose votes he badly needs. John McCain and Bob Corker are both the kinds of wavering Republicans that the party ought to be able to corral. They have made noises about fiscal responsibility in the past, but both are also generally reliable votes in party-line scenarios, with McCain’s defection on health care being an obvious exception.

After McCain gave a speech denouncing “half-baked, spurious nationalism,” a conservative talk-show host goaded the president to respond yesterday. Trump naturally obliged. “Yeah, well I hear it. And people have to be careful because at some point I fight back,” he said. “I’m being very nice. I’m being very, very nice. But at some point I fight back, and it won’t be pretty.” So the strategy is to turn this into a test of manhood with a war hero who’s dying of cancer and clearly seeking a glorious end to his political career? Good plan!

Meanwhile, Trump has decided simultaneously to revive his vendetta with Corker, who has made cutting remarks about Trump’s capacity to handle foreign policy. Corker has said he won’t vote for any legislation that increases the deficit. On the other hand, he approved a budget deal that would allow a $1.5 trillion increase in the deficit, and it’s entirely plausible he could be mollified with vague promises that tax cuts will produce more growth (and, hence, revenue) than mainstream economic models predict.

Corker has always played nice with his party. Does he really want to end his career by supplying a decisive vote to kill their main legislative priority, and in so doing, precipitate a failure they claim will bring on a midterm election rout? Trump is trying to find out!

Bob Corker, who helped President O give us the bad Iran Deal & couldn't get elected dog catcher in Tennessee, is now fighting Tax Cuts.... — Donald J. Trump (@realDonaldTrump) October 24, 2017

...Corker dropped out of the race in Tennesse when I refused to endorse him, and now is only negative on anything Trump. Look at his record! — Donald J. Trump (@realDonaldTrump) October 24, 2017

Corker is naturally indicating a lack of interest in backing down:

Same untruths from an utterly untruthful president. #AlertTheDaycareStaff — Senator Bob Corker (@SenBobCorker) October 24, 2017

You gonna take that, Donald? Huh?

Republicans have 52 votes in the Senate. Minus McCain and Corker, they have zero margin for error. They would need every other vote, including Susan Collins’s. Trump may believe that his social-media bullying campaign is an effective way to prod recalcitrant members of his party into line. It has certainly worked many times before — his crude insults of people like Ted Cruz and Marco Rubio resulted in their eventually submitting. But Trump may not be distinguishing between young pols on the make and retiring senators who have nothing to lose.