2. Seize the debates.

There are a dwindling number of opportunities for Mr. Trump to change the dynamics of the race, and the debates are Nos. 1, 2 and 3 on that list. They offer Mr. Trump a huge audience to appeal to this year’s swing voters: people who don’t like Mrs. Clinton but are afraid of a Trump presidency. “Trump has to show that he is acceptable,’ said Neil Newhouse, a Republican pollster. “Right now, looking at the numbers, he is not. It’s not the message but the messenger that’s holding some of these voters back.”

3. It’s about Clinton.

Mrs. Clinton is trying to make this a referendum on Donald Trump, and on many days Mr. Trump seems to be doing his best to help her. Instead, Mr. Trump should turn this into a discussion of Mrs. Clinton. There is a receptive audience for change among voters tired of eight years of Democratic rule and 25 years of the Clinton family.

Rather than spending two weeks wrestling with immigration, Mr. Trump might have been better off talking about the Clinton Foundation, or Mrs. Clinton’s email troubles. Every day. Repetition, repetition, repetition can be boring, especially for someone like Mr. Trump. But that’s the way to win an election.