I’ve nevertheless detected a lot of consternation among Clinton voters: Why isn’t her position safer? There’s really about a 35 or 40 percent chance that Trump will become president?

Based on the polls, we think the model is setting those odds about right. The race is a long way from being a toss-up, but a 3 or 4 percentage point lead heading into the conventions isn’t all that reliable, either. While Obama won twice with pre-convention leads of about that margin, John Kerry went into his convention with a lead of about 3 percentage points in 2004, but lost to George W. Bush. And in 2000, Bush had about a 4-point lead on the eve of the conventions, but lost the popular vote to Al Gore. (Bush won the Electoral College, of course.)

The flip side is that the recent polls could just as easily prove to be a low-water mark for Clinton. Conventions have oftentimes helped the incumbent party’s candidate. One of the biggest turnarounds came in 1988, when Michael Dukakis, the upstart winner of the Democratic nomination, held a lead of 6 or 7 percentage points going into the conventions. But a well-staged Republican convention in New Orleans helped to unify the GOP and highlight the successes of George H.W. Bush and Ronald Reagan, and Bush eventually won by a landslide.