There’s an obvious reason. What I can’t figure out is whether the numbers here are strong evidence that Democratic leaders do have serious influence over the rank-and-file’s views — or that they don’t.

The decline — from 43% in favor in December to 36% now — stems largely from a change in Democratic views on impeaching the President. In December, 80% of self-identified Democrats said they were in favor of impeachment — that now stands at 68%, a 12-point dip. Among independents and Republicans, support for impeachment has fallen 3 points over the same time.

The only major subgroup among which the decline was larger than among Democrats is college graduates: 50% backed impeachment in December, 35% do so now. Combining the two to look at Democrats with college degrees, support for impeachment fell 17 points from 79% in December to 62% now

Overall, the share of Americans backing impeachment for Trump is the lowest level found since CNN began asking about it last June. Support had been as high as 47% last fall.

What accounts for the change? Simple: Nancy Pelosi finally went on record to say she’s opposed to impeachment and was backed up by the likes of Adam Schiff. Democrats with college degrees are exactly the sort of demographic you’d expect to follow pronouncements from Democratic leaders in Congress and, sure enough, here they are rapidly cooling to the idea now that Pelosi’s signaled her disapproval. Irony of ironies, Trump’s nemesis killed impeachment fever on the left!

Well, maybe not killed. Wounded, let’s say. Slightly wounded. Superficially wounded. What I meant up top in wondering what this says about her influence is that Democratic support for impeachment is still awfully high despite the Speaker’s apprehension. Progressives like AOC and Tom Steyer demand impeachment; the most powerful Democrat in the country, renowned for her political acumen, calls it a bad idea. And a supermajority of Dems *still* side with the former over the latter in wanting Trump gone. Even the college-educated segment of the party wants him out at a 62 percent clip.

Can Pelosi really hold back that tide, especially if Mueller’s report hints at obstruction of justice?

On the other hand, fascinating historical numbers from the crosstabs:

Both Dubya and Obama had greater shares of the public in favor of impeaching them than Bill Clinton, who actually was impeached, had. Until recently Trump had them all beat, routinely pulling above 40 percent on the impeachment question. A CNN poll taken in September put that figure at 47/48, perilously close to majority support. Now, however, thanks to Pelosi’s dim view of the prospect, Trump stands at 36/59 on impeachment, the lowest share yet — and only slightly higher than Bush or Obama.

By piping up in opposition, Pelosi has actually helped create the outcome she favors here. The higher public support for impeaching Trump is, the less power she’ll have to hold back her caucus from doing it. By coming out against the prospect, she’s driven public support down to the point where it may be impossible for impeachment diehards on the left in the House to muster the political will to follow through.

Maybe there’s more to the overall drop in support for impeachment than just Pelosi’s influence, though. This is actually the second straight poll in which support declined: It went from 47 percent in September to 43 percent in December to 36 percent now. To rephrase that, it was at an all-time high before the midterms, then dipped after Democrats won back the House in November, then dipped even more sharply after they actually took power in January. The more abstract the prospect of impeachment is, in other words, the more gung ho Dems are to do it. Once the prospect became feasible, carrying with it the possibility of an electoral backlash if they followed through, it may be that some squishy impeachment supporters began to get cold feet. Notice that support for impeaching Obama dipped a bit after the 2014 midterm in the table above even though that election gave the GOP control of the Senate, increasing the possibility that it might actually happen.

To some degree, impeachment fever is driven by the out-party’s frustration at being locked out of power. The president beat you at the polls, you’re spoiling to get some leverage over him and over national policy, so naturally thoughts turn to ways he might be lawfully removed. Win a congressional election, though, and you no longer need to impeach to have some policy influence. If Trump were to win next year and Democrats were to reclaim a Senate majority (a highly unlikely outcome), we might see Dem support for impeachment decline further even though, seemingly paradoxically, they’d be in a better position to make it happen. More influence over government means less interest in a desperation move like impeachment to impose your political will.

Needless to say, though, that argument overlooks the fact that Mueller is the biggest X factor in modern political history. All questions of partisan influence and leverage aside, if his report is accusatory Democratic impeachment fever will turn critical. Not even Pelosi will be able to stop it.