Nor is the assumption that these stories won’t matter with voters particularly well-founded. It is of course true that the story won’t matter with Trump’s hardcore base — but that is beside the point. All presidential candidates, even the losers in the biggest landslides, deliver their party’s base voters; that’s what makes them base voters. Trump needs voters who aren’t his base, and while the number of undecided swing voters is relatively small, they’re outsize in importance.
The assumption that the story won’t matter is particularly strange when you remember that the outcome of the 2016 election was almost certainly changed by James Comey’s decision to announce the temporary re-opening of the investigation into Hillary Clinton’s email management practices. This is not, as Nate Silver observed in his deep dive into the subject, because it changed the minds of a particularly large number of voters, but because the extra point of two Trump gained from the late tsunami of negative coverage about Clinton made a big difference to the outcome of an election decided by 80,000 votes in three states. (And in an election that close, many other relatively small events and decisions that can’t be as easily measured could have altered the outcome.)
If a story about Hillary Clinton’s email server management could change an election’s outcome, why not a story showing Trump is a fraud as both a businessman and a taxpayer?