Friday morning began with even-unusual-for-President-Trump tweets disparaging special counsel Robert S. Mueller III and his investigation into Russian interference. Over the course of about an hour, Trump dropped five tweets, bashing Mueller, the attorneys working with him, Hillary Clinton and so on.

But you know this. You’ve heard about these tweets or seen them. Five drops of tweeted water, slipping off the collective anatine backs of the American public. That’s just what Trump does, right? He gets mad about Mueller and tweets things, and the great wheel of life keeps ticking forward without interruption.

It raises a question, then: Are Trump’s tweets persuading anyone? Happily, we have polling that can shed some light on this issue.

Quinnipiac University has been polling Americans about their views of the fairness of the Mueller probe for more than a year. Over that time, there has been a decline in the number of Americans saying the investigation is fair, from 60 percent in November 2017 to a bit over 50 percent in August, when the most recent poll was taken.

(Philip Bump/The Washington Post)

As you can see, that’s mostly a function of Republicans turning against the probe and some erosion among independents.

Notice that big jump in the percentage of Republicans saying that the investigation isn’t fair in about the middle of the chart. That occurred from the beginning of March to the end of April. The cause?

Well, on March 17, Trump for the first time mentioned Mueller by name in a tweet.

(Philip Bump/The Washington Post)

Perhaps that spurred his base to increasingly view Mueller with skepticism. (Quinnipiac’s question includes Mueller’s name.) Since that spike this spring, Republican views have remained fairly flat.

Let’s consider another factor that might be influencing people. Suffolk University released a poll in October that shows how members of each party view the probe. Three-quarters of Democrats say they have a lot or some trust that Mueller’s investigation will be fair. More than half of Republicans say they have little or no trust that it will be.

(Philip Bump/The Washington Post)

Suffolk also asks another useful question that we can use to compare responses: What’s your most trusted news or opinion source? When we cross-reference that with the question about fairness, another point of influence emerges.

(Philip Bump/The Washington Post)

Views of the Mueller probe are more positive among people who trust MSNBC and CNN most than are views of Democrats overall. And, significantly, Mueller is much less trusted by those who trust Fox News the most than he is by Republicans overall.

Fox News is also the most trusted outlet in Suffolk’s polling — because it’s the overwhelming choice of Republicans. There’s a mutual reinforcement: Republicans like Trump, and they like Fox, and Fox often focuses on information Republicans will like or plays down news that casts Trump in an unfavorable light.

A poll in July found that Trump’s favorability was higher among those not paying much attention to the Russia probe. Fox had, to that point, spent much less time than its competitors on the subject.

Polling aside, there’s an intuitive reason to think that Trump’s tweets about Mueller aren’t having much effect. Find me the American who has yet to make up his or her mind about Mueller and who will be persuaded by the most recent iteration of Trump’s rhetoric on the subject. In Suffolk’s poll, 9 percent of Americans said they hadn’t heard of Mueller. For reference, an August NBC-Wall Street Journal poll found that 10 percent of Americans hadn’t heard of House Minority Leader Nancy Pelosi (D-Calif.).

The odds that this 9 percent of the country will suddenly take a keen interest in the subject that’s dominated political news for 20 months and be persuaded by Trump seem ... low.