Mr. Rubio can recover. He began the process in his concession speech Tuesday night by acknowledging that he didn’t do well in Saturday’s debate. No one has worked harder during this election cycle than Mr. Rubio to tell a generational story about restoring the promise of America. His campaign has focused on reinforcing this message at every speech and in every interview, and many voters are still drawn to the prospect of a general election that pits Marco Rubio against Hillary Clinton or Bernie Sanders. We would flip the script on the Democrats and be the party to offer the fresh-faced leader with a clean slate.

Until recently, Mr. Rubio’s team has avoided getting bogged down in process. Process stories are a black hole of struggling campaigns. His campaign is smart enough to know that this is where real message discipline comes in. Mr. Rubio now needs to prove his detractors wrong on the charge that he clings to a script because his knowledge of policy is too thin to freestyle.

The Republican Party has rewarded Mr. Trump handsomely for his aversion to even a nanosecond of scripted political contrivance, and he doesn’t possess a fraction of Mr. Rubio’s knowledge of foreign policy. Conservatives want gut players with backbone. Mr. Trump says the wrong thing more often than he says the right thing, and the voters respond with growing affection. So why is Mr. Rubio sticking to rehearsed one-liners? This is an election about shredding the script.