President Trump earned a few headlines over the past two weeks that almost certainly annoyed him.

Talking Points Memo, for example, looked at Gallup daily approval ratings for the president and noted that his net approval — those who said they approved of his job performance minus those who said they disapproved — moved from even to minus-8 over the first week of his presidency. The Los Angeles Times took a different tack, noting that weekly averages of presidential approval give us a better comparative sense of how Trump is faring.

Those numbers, made available by demographic group, let us see what changed for Trump over the first two weeks of his presidency. The upshot? Groups that disliked him drove his overall numbers lower as their perceptions of how he was doing fell further.

That it’s Trump skeptics whose opinions soured isn’t exactly good news, mind you. Conservative Democrats saw the biggest downward shift; that’s a group from which Trump has consistently argued he pulls unusually high support. (It’s also a fairly small demographic group, so that probably accounts for some of the fluctuation as well.) Likewise, those with only a high school education now look at how Trump is doing more negatively. That Republican approval ratings of Trump’s job performance fell three points is probably more disconcerting still.

Between his first and second week, President Barack Obama also saw a decline in his approval rating. The drop was less uniform than Trump’s, and the overall drop was smaller, though the statistical difference between a two-point and one-point decline is nonexistent. Obama also saw a dip among his opponents, but those opponents had a better view of him than Trump’s do now.

Perceptions of Obama among conservative Democrats increased significantly.

In fact, Gallup has weekly averages for the past four presidents, and in three of those four cases the change between the first two weeks was downward. New presidents get a honeymoon period of some sort and that fades quickly.

What’s remarkable about that graph is not the decline, it’s where Trump started out in the first place. Of the 418 weeks Obama was president, he was at or below 43 percent — Trump’s current approval rating — for only 52 of them. One-eighth, in other words.

We don’t remember Obama’s presidency as being one in which he was robustly and consistently popular — but he was almost always more positively viewed than Trump is now. Gallup found that his average approval rating over his term placed him ninth among the 12 most recent presidents.

How bad are Trump’s approval ratings? Approval of Obama by conservative Republicans in the first weekly Gallup average in 2009 was higher than Trump’s approval now from people under 30, those with a post-graduate degree, Democrats, and people on the east and west coasts. And conservative Republicans were his worst-performing group.

No wonder Trump hates polls.

The trend to watch is if Trump’s base continues to erode. Further erosion of Republican approval, or more negative attitudes from those without college degrees, will mean that Trump’s already-weak base is growing weaker. That’s the story: It’s not that Trump’s base shrunk, it’s that he’s running out of base.