Well, maybe this one does. Photo: Andrew Lichtenstein/Corbis via Getty Images

Donald Trump says that the special counsel’s investigation into Russian interference is “the single greatest WITCH HUNT in American political history” — one led by “very bad and conflicted people.”

A good chunk of his voters beg to differ. A CBS News poll released Tuesday finds that a plurality of Republicans believe Robert Mueller’s probe will be “impartial,” while 75 percent believe that the president should not try to stop the special counsel’s investigation.

That said, more than half of Republicans say the investigation is a “political distraction that should be put aside.” And the vast majority say that the various Russia investigations have not changed the way they view the president — while 11 percent of GOP voters say the probes have made them think better of Trump.

But to win reelection, the president will need to retain more than the “vast majority” of his base. Trump’s approval numbers with Democrats and independents have always been exceptionally low. He was able to win last fall’s election — and then keep his favorability around 40 percent — on the strength of his support from Republican voters.

Now, the Russia probe appears to be eroding Trump’s base. The president’s approval rating is down to 36 percent in CBS’s poll, the worst mark he’s ever posted in that survey. And disappointed Republican voters bear much of the responsibility for Trump’s decline.

At the end of April, 83 percent of Republicans told CBS they approved of the president; this month, that figure fell to 72. And the Russia probe seems to be the primary reason why: Fifteen percent of Republicans say the investigations have made them think worse of Trump, while only 57 percent approve of how the president has “handled” said investigations (i.e., interfering in federal investigations, confessing to obstruction of justice on national television, engaging in witness intimidation over Twitter, et cetera).

Nearly a quarter of Republicans say they trust James Comey more than Trump, while 40 percent believe it is at least “somewhat likely” that the president’s associates had improper contact with the Russian government during the 2016 campaign.

CBS is far from the only pollster to detect a decline in Trump’s base of support since the Russia story began dominating the headlines in the wake of Comey’s firing. On the day that the FBI director was dismissed, FiveThirtyEight’s poll aggregator put his approval rating at 42 percent. Today, it sits at 38.6. And as Nate Silver noted in late May, the quality of Trump’s support has declined along with its quantity.

There’s been a considerable decline in the number of Americans who strongly approve of Trump, from a peak of around 30 percent in February to just 21 or 22 percent of the electorate now. (The decline in Trump’s strong approval ratings is larger than the overall decline in his approval ratings, in fact.) Far from having unconditional love from his base, Trump has already lost almost a third of his strong support. And voters who strongly disapprove of Trump outnumber those who strongly approve of him by about a 2-to-1 ratio, which could presage an “enthusiasm gap” that works against Trump at the midterms.

There’s been some debate in progressive circles about whether attacking Trump for his health-care bill is more effective than savaging him over his Russia ties, and apparent attempts to obstruct justice — or vice versa.

The available data suggests a decisive answer: