Donald Trump is on the fast track to approval depths last plumbed by George W. Bush, or at least that’s what many Democrats hope. RealClearPolitics has his approval at 41.1 percent — and trending downward.

But without a major change in the political environment, Trump’s ratings won’t sink that much lower. Why? Because he has already burned off the public benefit of the doubt normally afforded to new presidents. In other words, those that could disapprove of him because of his clownish behavior or rank bigotry already do.

Any further decrease in his popularity will have to come from disaffected Republicans and conservative independents.

Until the health-care debacle, this was an unlikely prospect. But now it may be inevitable.

Historic lows

Gallup has Trump’s approval at 38 percent today and 35 earlier this week. This is unusually low by historical standards. At this point in his presidency, Barack Obama had an approval rating of 62 percent. The average for presidents in their first-year first quarters is 63 percent approval. Jimmy Carter even polled at 72 percent two months into his presidency.

There is a reason for these sky-high numbers: Americans want to like their new leaders.

Astonishingly, 37 percent of Democrats supported George W. Bush at this point in 2001 — and that was after an acrimonious 2000 election and recount.

Trump thoroughly poisoned the well long before his inauguration in January. He ran a preposterous, racist and antagonistic campaign. His transition was ideologically excessive for having won the election by a margin of -2.1 percent. And his initial volley of executive actions seemed designed to aggravate the left — and anyone who had doubts about him.

Here’s the result of that extensive operation: only 8 percent of Democrats and a third of independents approve of Trump’s job performance. In January, those numbers were 13 and 42, respectively. (Notably, Trump won independents by 46 to 42 points — how times change!)

Republicans are loyal, for now

Republicans are different. They have supported Trump at a rate of 84 percent or more through each week of his presidency.

Any why not? Up until now, Trump has been a pretty good Republican. His cabinet appointments, executive orders and budget proposals are all far-right. His hostile behavior toward liberals unites Republicans of all stripes.

Yet we know from the campaign that Trump does not enjoy universal support in his own party. Recall that he secured the nomination after one of the most bitter presidential fights in modern political history. Every single Republican candidate took firm positions against him. There were even moves to unseat Trump at the convention.

With that in mind, President Trump will soon learn that giving his supporters catharsis via tweeting can only take him so far. As party leader, he actually needs to get things done.

President Obama was able to draw on the accomplishments of 2009-10 and maintain his popularity among Democrats during his last six years in office, when Republicans blocked his domestic policy agenda.

If Trump does little more than shuffle staff at federal agencies and launch rhetorical broadsides at “fake news”, he will have broken the promise he made to those Republicans who swallowed their loathing of him so as to beat Hillary Clinton.

The results so far? Not good

Republicans voted dozens of times to repeal the Affordable Care Act. It likely cost Democrats control of the House in 2010. Ted Cruz shut down the federal government in 2013 to try to kill the law.

Trump understands this hatred of Obama’s signature accomplishment: He repeatedly and unequivocally promised repeal and replacement on the first day in office.

Not surprisingly, he failed to make good on that vow. And when he did start to examine the issue weeks in, he found that health care was, in fact, “hard.” (Who knew?) His effort collapsed and rather than taking responsibility or moving forward with a new bill, Trump accepted the existence of Obamacare.

If Jeb! had engaged in this type of capitulation via incompetence, Trump would have lambasted him for being low-energy.

Instead, we’re seeing a deflated, patently miserable Trump more interested in litigating inauguration numbers and wiretapping delusions than in exerting the mental or physical energy to generate any sort of policy.

Wrong lesson

Trump has learned the wrong lesson from all of this. Unsatisfied with providing a mere lack of conservative leadership, he has chosen instead to go after his own — particularly the Freedom Caucus, which he has lambasted ever since the health-care defeat.

By shining a massive tweet-fueled spotlight on this group of ultraconservatives, Trump is fueling a ready-made vehicle for right-wing opposition to his presidency. Expect the Freedom Caucus to become a rallying point for anti-Trump conservatives, even if bandwagon members don’t agree with all of the group’s far-right positions.

Ultimately, Trump needs to fire up conservatives who opposed him. The red-meat flights of fancy he throws to red-hat-wearing true believers isn’t going to do the trick with the rest.

Otherwise, the next ones to flip will be conservatives. They’re the only ones left.