This poll had Clinton leading by just 3 points last month, now the gap is up to 15 points. From McClatchy:

Clinton not only went up, but Trump went down. Clinton now has a 48-33 lead, a huge turnaround from her narrow 42-39 advantage last month.

Clinton gained 6 points while Trump lost six. That divide created the largest lead yet recorded for Clinton in a national poll. Looking more closely, part of the shift was Republicans backing away from Trump but Clinton also cut into his advantage with men and has almost erased his lead among white voters:

Trump gets the nod from just 79 percent of Republicans, down from 85 percent last month…

Men had been the bedrock of Trump support. Last month, he was up by 14 percentage points among men; he’s now down 8. Clinton remains strong with women, as she’s up 20…

Even among white voters, which favored Republican White House candidates in recent elections, Trump was lagging, ahead of Clinton, but only just barely, 41-39.

While this particular poll may be an outlier, yesterday Fox News gave Clinton a 10 point lead over Trump, 49-39. The Real Clear Politics average of national election polls (which does not include this McClatchy poll yet) has Clinton up 5.8 points based on polls taken over the past week.

There are still three months to go before election day. That’s a lot of time for these numbers to change as a result of either Trump’s numbers coming back up or Hillary’s coming back down or both. Hillary’s could come down very quickly as the result of a gaffe, an embarrassing email leak or an incident in the real world such as a terrorist attack which causes voters to reassess their priorities.

On the other hand, Trump’s numbers could go up if he becomes more disciplined and stops picking fights that erode his support. For instance, his pointed decision not to endorse Paul Ryan is not going to help him win Republicans back to his camp. He may not like that needs the support of other Republican leaders to win but he does.

In fact there’s reason to think even some of the support Trump has now is tenuous. The McClatchy poll finds that 40% of Clinton voters are voting for her because they are against Trump rather than because they are pro-Clinton. That’s not a very strong endorsement of Clinton, obviously. But on the other side of the aisle 57% say they are against Clinton rather than because they are for Trump. Those voters won’t stop being against Hillary no matter what Trump does but the fact that they are not Trump die-hards means they could decide to stay home, especially if it looks like Hillary has a commanding lead.

The outcome of this election is not completely in Trump’s hands but some of it is. As Newt Gingrich said this week, Trump has, “thrown a series of interceptions.” He can and probably will do better in the polls but that starts with him not being self-destructive.