Is Trump doing a good job as president? At his exhausting/tive news conference Thursday, he suggested that he was, pointing to a recent survey from Rasmussen Reports that showed him with 55 percent approval. Over the course of 2016, though, Trump developed a bad habit of cherry-picking poll results that cast him in a favorable light, and that’s where Rasmussen falls. There have been 138 polls of Trump’s job approval since he took office; in 42 of those, he’s at or above 50 percent. That’s better than his favorability numbers, to be sure, at 30.4 percent. But it’s also the minority.

The gold standard of approval ratings is compiled by Gallup, the firm that helped create public polling and that has been sampling America’s opinion of its presidents since Franklin D. Roosevelt. Gallup compiles daily running and weekly averages that it used to track how popular presidents are. By neither metric is Trump doing very well.

We’ve noted before that Trump’s got record-low approval ratings, but as time has passed those ratings have only gone down. Gallup’s daily rolling average shows a widening gulf between the number of people who think he’s doing a good job and those who don’t. More than half the country has disapproved of the job he’s doing since Feb. 4.

That can be a little misleading though, because there’s a lot of daily variability. Looking at weekly figures, Trump’s doing better — mostly because this week’s average hasn’t been calculated yet. (New figures come out Sundays.) As of the beginning of this week, though, he was at 41 percent overall approval. That’s a percentage that’s higher than only 12 weeks that Barack Obama was president. Put another way, 97.1 percent of the time, Obama’s weekly numbers were higher than Trump’s most recent average.

Gallup also has overall high and low poll ratings for every president since Truman. Where Trump is in his daily average — 38 percent — is lower than presidents Dwight D. Eisenhower or John F. Kennedy ever got. But it’s also as low as Obama ever saw.

Obama and Trump served in office at a time when the electorate was deeply polarized, as we’ve noted. That helped Obama keep from seeing numbers that were too low; Democrats never bailed on him. Trump’s starting off with lower support from his own party and much lower support from the opposition.

It’s not the case that the percentage of the population that views Trump as doing a good job is lower than the percentage of the country that voted for him. Yes, he got 46 percent of the vote, and only 38 percent of the country thinks he’s doing a good job, but a lot of Americans didn’t vote, as this chart from mid-November makes clear.

For Trump’s approval rating to be low enough to mean that even his core base of support is necessarily frustrated with how he’s doing, he needs to hit about 27 percent (excluding those who aren’t eligible to vote). It’s … maybe possible. But it would mean a big erosion among Republicans.

One interesting footnote, picked up by Charles Franklin.