Notice what's happening to broaden Clinton's lead in the RealClearPolitics average: Trump is sinking as much as Clinton is rising. Her lead in the polling average is now nearly as big as it was after the Democratic convention. He's got a core base of support that flexes upward on occasion, but only temporarily. It keeps retracting.
A new survey from The Atlantic and PRRI reinforces where the most recent retraction has occurred. Clinton leads Trump by 11 points in the new poll, up from a 6-point lead last week and from a tie two weeks ago. The poll overlaps only partially with the hot-mic tape story (about half of the interviews were conducted after the news broke) so it's still hard to parse that out specifically.
One big shift, though, is with women. In the poll two weeks ago, women preferred Clinton by 10 points. Now, they prefer her by 33 points. Trump's support from men has remained unchanged.
One other big shift is among independent voters, continuing a trend that we noted last week. A week ago, independent voters preferred Trump by 8 points; now they prefer Clinton by 11.
Independents have usually favored Trump in polling, but the margin between how strongly they prefer Clinton or Trump predictably correlates to the margin between the two candidates.
There's a stronger correlation, though, between how strongly each candidate is supported by members of their own party. Since Sep. 1, Clinton's consistently gotten more support from Democrats than Trump has from Republicans, and that is tied to her lead in the polls.
We've consistently seen that softer support from Republicans has been a factor in Trump's poll slides. In this Atlantic-PRRI poll, for example, 90 percent of Democrats back Clinton while only 85 percent of Republicans back Trump. The two get about the same support from members of the other party, but that gap helps explain a lot of Trump's overall problem.
Why the gap? Because Republicans and independents seem to be getting turned off by Trump. His failure in the first debate and the sketchy hot-mic tape might be pushing his numbers lower, shedding some of the additional people he'd added to his core base of support. More Republicans voted for someone besides Trump in the primary than voted for Trump. His ability to keep all of those voters on his team has proven shaky. Trump simply hasn't figured out how offer a consistent message that can to appeal to those folks or to Republican-leaning independents.
Now, with four weeks left, he seems to have one last idea: Appeal even more to that core base of support. One might normally call this preaching to the choir, but let's revisit the metaphor we led with: Trump's strategy looks a bit less like Sherman's march than it does a retreating army trudging back to its burning capital, deserters left behind in the snow.