Washington (CNN) President Donald Trump, as you may have noticed during his two years in politics, is an avid consumer of polls -- especially when they make him look good.

Fifty percent! That's not bad! Particularly given how much negative press Trump gets, according to Trump.

I was intrigued about the Rasmussen result, so I did a bit of digging and also reached out to CNN polling czar Jennifer Agiesta for her take.

There are a few reasons to be skeptical about the Rasmussen result.

* Rasmussen surveys "likely voters" in their daily approval polls. They argue it gives them a more accurate reading of the actual voting electorate -- and certainly a more accurate one than polling firms that test all adults. The problem, according to Agiesta, is that we have no real idea of how Rasmussen decides who a "likely voter" is. Is it based on the 2016 election? 2012? Some combo? Rasmussen won't say. ( Here's what Rasmussen does say about its samples .)

* Rasmussen used an automated voice (as opposed to a real, live person) to conduct their polls. They are, therefore, barred by law from contacting people on cell phones. People who only use cell phones tend to be younger and more diverse than those who have landlines. And younger, more diverse voters have heavily favored Democrats in recent elections.

* Rasmussen doesn't disclose how they conduct the telephone portion of their surveys. (They also do an online poll as a supplement to their phone results, which is a whole other problem.) Most pollsters use a technique called random digit dialing , which is exactly what it sounds like, to build a representative sample. Others -- particularly partisan pollsters -- poll off a privately maintained voter file. (More on that here .) Which one does Rasmussen use? We don't know if they use either -- or some other way to develop a random sample of the public -- because they don't release details on how they do it.

There are other, even more technical and nerdy reasons why you should be somewhat skeptical of Rasmussen, but you get the idea. In an industry in which transparency is the name of the game, Rasmussen just doesn't show very much of how they do what they do. That's not to say what they do is wrong; it's only to say we have no way of knowing how closely they adhere to accepted polling standards.

(Worth noting here: Rasmussen was one of the pollsters who came closest to getting the 2016 results right -- as they noted shortly after the election .)

What Rasmussen may be picking up -- and this tracks with Gallup's findings as well -- is that after hitting a low point in his job approval at the start of this month, Trump has been tracking upward. Rasmussen measured him at 42% approval on April 3 while Gallup had Trump's weekly average at 38% as of April 2. Both polls suggest gains for Trump since then; the difference is that Trump started off higher in Rasmussen than in Gallup.

The rise in Trump's approval numbers tracks closely with his decision to strike a Syrian air base that US officials say was the staging ground for a chemical attack by that country's government on its own people. That strike took place Thursday, April 6.

The larger point here: No one poll should be taken as the "truth" about where Trump -- or any other politician -- stands. Polls are, by their nature, snapshots in time. That's how we all -- and, yes, this means you, President Trump -- should be treating them.