Donald Trump has convinced himself he’s an extraordinary success. His constituents don’t seem to agree.

President Trump’s standing with the American people has deteriorated since the spring, buffeted by perceptions of a decline in U.S. leadership abroad, a stalled presidential agenda at home and an unpopular Republican health-care bill, according to a new Washington Post-ABC News poll. Approaching six months in office, Trump’s overall approval rating has dropped to 36 percent from 42 percent in April. His disapproval rating has risen five points to 58 percent. Overall, 48 percent say they “disapprove strongly” of Trump’s performance in office, a level never reached by former presidents Bill Clinton and Barack Obama and reached only in the second term of George W. Bush in Post-ABC polling.

To help drive the point home, I put together the above chart, relying on data from Washington Post, ABC News, and Gallup, to show every president’s public standing after six months in office since the dawn of modern American polling. Trump isn’t just unpopular; he’s unpopular in ways we haven’t seen in modern times.

But that’s not new. What is new is the president commenting on his woefully weak public support.

“The ABC/Washington Post Poll, even though almost 40% is not bad at this time, was just about the most inaccurate poll around election time!” Trump declared via Twitter.

For now, let’s put aside the fact that Post/ABC poll was actually quite accurate in 2016. Let’s also be charitable and look past the unintentionally amusing idea that a 36% approval rating is somehow “almost 40%.”

Instead, the part of the response I found interesting was the idea that Trump believes his weak public support is “not bad.”

It is, in reality, quite bad, indeed. None of the president’s modern predecessors have been in this position, and opposition to Trump has reached levels Obama and Clinton never saw at any point in their years in the Oval Office. The result is a flailing, scandal-plagued president with no credible claim to political capital after just six months in office.

What’s more, this is a White House without any real buffer: Trump’s support is below the 40% threshold despite low unemployment and decent economic growth. If the economy stalls, or there’s an unforeseen crisis that rattles the public’s confidence, it’s easy to imagine the president’s approval rating collapsing further.

Common sense suggests a political leader and his team, faced with this data, would start considering some kind of course correction. After all, there’s quantitative evidence that most Americans just aren’t buying what this president is selling.

But that won’t happen – because as far as Trump is concerned, being historically unpopular “is not bad.”

Congressional Republicans, most of whom will face voters two years before the president will, should feel quite a bit of anxiety about such a posture.