If your only source of information about President Trump’s approval rating is President Trump’s Twitter feed, you’re likely under the impression that it’s skyrocketing.

After all, on March 28 he tweeted an image showing his approval at 50 percent in Rasmussen Report’s (consistently Trump-friendly) polling. On Tuesday, Rasmussen had Trump at 53 percent. And then, on Thursday, a stunning 55 percent in a poll reported by Fox Business’s Lou Dobbs. Unfortunately for supporters whose information about Trump’s popularity comes from his tweets, that last number was actually Trump’s unfavorable rating in the cited poll. His approval was a more modest 43 percent.

But even 43 percent isn’t bad for Trump. On Friday morning, Gallup reported that Trump’s approval had jumped to 45 percent in its polling, only the third time it’s been that high. The other two moments were at his inauguration and in mid-June 2018, at about the time of his summit with North Korean leader Kim Jong Un.

It’s worth noting, though, how little Trump’s approval rating has actually ranged since he’s been in office. That 45 percent approval is one of three times it’s been that high, at the upper end of a range that only extends over 11 percentage points. Four times in Gallup’s polling he’s been at 35 percent, the opposite end of the spectrum. Just up and down, from 35 to 45.

The reason for this isn’t a secret: Trump’s consistent support from Republicans and consistent opposition from Democrats has largely anchored the poles of his support. Independents move around a little, making up much of the change. The jump to 45 percent in the recent poll, for example, is in part a function of his gaining six percentage points in his approval from independents. But, in the exception that proves the rule (or something), it’s also in part a function of his doing better with Democrats.

The narrowness of the range of Trump’s approval ratings stands out when compared to past presidents — with one exception.

George W. Bush’s approval, for example, ranged over 70 points, a function of his post-9/11 popularity and ensuing post-Iraq unpopularity. Barack Obama’s approval, like Bill Clinton’s, ranged over 28 points — but only because he had a brief honeymoon period at the beginning of his presidency. After that, Republican opposition to Obama hardened, and he, too, saw approval ratings that stayed only within a narrow range.

It’s not solely a function of Trump’s not having yet served a full term. John Kennedy, who served about seven months more than Trump has to this point, saw his approval rating range over 28 points. In a world where partisanship was more fluid, approval ratings could move more.

That’s why Trump’s insistences that he’s at 50 percent approval or higher — a level of support he’s never seen in most non-Rasmussen polls — should inspire skepticism. Unless he’s winning over a lot of Democrats (seemingly unlikely) or a ton of independents, he’s not going to see a big boost in his approval numbers. We’ve scaled our expectations down to the point that his, again, reaching 45 percent seems . . . not bad. He’s tied with his highest approval rating on record! It’s just that 45 percent is lower than the average approval rating in Gallup’s polling of every other president since Franklin Roosevelt.

At the upper end of Trump’s approval, in other words, it still isn’t very good. And it’s not clear how it might go much higher.