As the presidential election enters its final three months there are plenty of indications that one of the presidential tickets is doing everything it can to limit its ceiling with voters. Even before the Republican National Convention, the mathematical wisdom suggested that Donald Trump was going to need a surge in support from whites to challenge Hillary Clinton in November. But that demographic is at low tide for the Republicans. After a tumultuous couple of weeks that included a laundry list of high-profile errors, the Trump coalition appears to be retracting.

In the latest Fox News poll, Trump is leading white registered voters by 10 points, 49 percent to 39 percent. A new McClatchy survey recorded an even slimmer margin, 41 percent to 39 percent for Trump. He leads white non-college graduates by about 15 points in both studies.