When Republicans originally got behind Donald Trump, they figured that it wouldn't much matter that he wasn't remotely conversant with the details of public policy. He could sit in the Oval Office tweeting about how America was becoming Great Again, while the experienced and knowledgeable GOP members of Congress, under the wise and firm guidance of Paul Ryan and Mitch McConnell, would write the bills, pass them through both houses, and send them on to the White House for a signature. So much winning, and everybody wins.

But when they set about tackling their first big legislative priority — repealing and replacing the Affordable Care Act — they found that Trump had an ability, and perhaps even an eagerness, to sabotage them at every turn, even if it wasn't clear he realized it. And now it's about to happen to them all over again.

It sometimes appears that Trump would be happier if the presidency was just a figurehead position, like king of Spain or grand marshal of the Rose Parade. Indeed, he may have thought that's what it was; after 100 days on the job, he confessed that he was surprised to learn that being president of the world's leading military, economic, and cultural superpower was somewhat more complicated than running a brand-licensing business. "This is more work than in my previous life," he told an interviewer. "I thought it would be easier."

Given all the strain, he wasn't going to be bothered reading briefing books and boning up on white papers; according to one report, National Security Council officials learned that in the documents they gave him it was necessary to repeat his name in "as many paragraphs as we can because he keeps reading if he's mentioned." But that doesn't mean he won't be called upon for his thoughts when key policy changes are being debated. And that's where the trouble starts.

Republicans had a difficult task in the ACA repeal, which is that they had to get the public to buy a version of health care that would be much less generous than the status quo. Their philosophy demanded that the government step back from providing insurance and subsidies, which would necessarily be painful; the promise of a better future fueled by the wondrous magic of the free market might sound good in the abstract, but it's not quite as appealing when it means you just lost your insurance.

But instead of using his unmatched megaphone to make the case for this change, every time Trump opened his mouth he seemed to promise more government, more benefits, a gentler embrace from Washington, D.C. "We're going to have insurance for everybody," he said, no doubt sending Paul Ryan rushing to reread his dog-eared copy of Atlas Shrugged for comfort.

It was an echo of the rhetoric he used during the campaign, not just on health care but much more broadly. "I will give you everything," he said. "I will give you what you've been looking for for 50 years." It's not a message that fits well with a party that would rather smack you across the face and tell you to pull yourself up by your bootstraps, and it left Republicans with the leader of their own party making promises they had no intention of keeping.

Now history is repeating itself as they prepare to launch an effort to cut taxes on corporations and the wealthy. Trump is shooting his mouth off again, telling reporters this week, "The rich will not be gaining at all with this plan." Even though the plan has not been issued yet, everybody knows the rich will be gaining quite a bit. He even suggested that the rich might get their taxes increased: "I think the wealthy will be pretty much where they are ... If they have to go higher, they'll go higher." Yet the chances that Republicans will raise taxes on the wealthy are precisely zero. When the administration released a brief outline of its plan earlier this year, the Tax Policy Center ran the numbers and determined that those in the top 1 percent were in for an average tax cut of $271,340, while those in the top one-tenth of 1 percent would get an average cut of $1.4 million.

To most Republicans, that's just as it should be — justice demands that those noble job creators be relieved of the terrible burden of taxation. But now that Trump has said what he said, they'll all be confronted by reporters asking, "The president said your plan wouldn't cut taxes for the wealthy. So how do you explain what it actually does?" Squirming will ensue.

Why does Trump do this? As much as he's focused on pleasing his base and lashing out at anyone who criticizes him, he also has a deep need for approval. In the moment, he's likely to say whatever he thinks will please whoever he's talking to. He wants smiles and nods, good press coverage, the affirmation of everyone around him. And since he has no firm conservative philosophy to guide him, he says whatever sounds good.

So when he gets asked about taxes, he'll say whatever sounds like it will meet with acclaim, regardless of whether it has any relationship to what Republicans are actually trying to do. Which is going to make their job — convincing the public that a gigantic tax cut for corporations and the wealthy will cure the country of all its ills — a lot more difficult.