Donald Trump’s strategy in this campaign has been fairly clear from the beginning: Drive up Republican support among white voters in order to compensate for the GOP’s shrinking share among the growing nonwhite portion of the electorate. And Trump has succeeded in overperforming among a certain slice of white voters, those without a college degree. But overall, the strategy isn’t working. Trump has a smaller lead among white voters than Mitt Romney did in 2012, and Trump’s margin seems to be falling from where it was when the general election began.

Four years ago, Romney beat President Obama among white voters by 17 percentage points, according to pre-election polls. That was the largest winning margin among white voters for any losing presidential candidate since at least 1948. Of course, even if Trump did just as well as Romney did, it would help him less, given that the 2016 electorate will probably be more diverse that 2012’s. And to win — even if the electorate remained as white as it was four years ago — Trump would need a margin of 22 percentage points or more among white voters.

But Trump isn’t even doing as well as Romney. Trump is winning white voters by just 13 percentage points, according to an average of the last five live-interviewer national surveys. He doesn’t reach the magic 22 percentage point margin in a single one of these polls.

SUPPORT AMONG WHITES POLLSTER TRUMP CLINTON DIFFERENCE CNN/ORC 49% 40% +9 CBS News/New York Times 49 37 +12 Fox News 51 30 +21 Monmouth University 47 39 +8 Quinnipiac University 50 36 +14 Average +13 Trump leads with white voters, but not by enough Last five national live-interviewer polls as of Oct. 4

Trump’s less-than-overwhelming margins among white voters in the polls listed above are a big reason why all five surveys showed him trailing Hillary Clinton overall. In fact, Trump would be losing by a larger margin, but third-party candidates are getting support from younger and minority voters, so that Clinton is slightly underperforming Obama among these groups. But the magnitude of Clinton’s struggles with young and nonwhite voters isn’t anywhere big enough to cancel out Trump’s relatively poor showing among white voters.

Perhaps, it would be better news for Trump if he were at least trending in the right direction with white voters. But he’s moved backward compared with polls back in May and early June. Back then, Trump led Clinton by 17 percentage points, on average, among white voters. In other words, the longer white voters have had a chance to listen to Trump’s message, the more they have been put off by it as a group.

To be more specific, Trump is trading one type of white voter for another. Even as he piles up support among white men without a college degree, he’s on track for a record poor performance for a Republican among white voters with a degree. And right now, that tradeoff is a net negative for Trump, compared with Romney. If a ton of new white voters without a degree flooded into the electorate, that could change the math for Trump. But such a surge doesn’t look like it’s in the offing.