ANN ARBOR, Mich. — President Obama was feeling a little sentimental.

His shirt sleeves rolled up, his vowels slipping off the ends of his words, his last day on the campaign trail finally here, Mr. Obama soaked up an unseasonably warm autumn sun on a baseball field at the University of Michigan on Monday, and drank in the energy of his political finale.

“We’ve got one more day, Michigan — one more day,” he said, gazing out over a crowd of more than 9,000 at midday. But Mr. Obama was not quite ready for it to be over.

“This is gonna be my last” — he caught himself — “probably my last day of campaigning for a while.”

For Donald J. Trump and Hillary Clinton, Monday’s cross-country travels were all about tomorrow. For Mr. Obama, his travels here to Michigan, and then to New Hampshire and Philadelphia, were part victory lap and part nostalgia tour, as he was accompanied on Air Force One by some of his longest-serving aides, and was ushered in and out of rallies by the same U2 and Bruce Springsteen anthems that were the soundtracks of his campaigns.

But his core mission was to implore voters across the country to rally behind Mrs. Clinton on Tuesday, or see the values and ideals that fueled his rise and powered his agenda defeated. So Mr. Obama stumped on Monday with the fervor of a man battling to preserve his legacy and with the joy of one who has watched his approval ratings tick higher as the presidential race’s tenor has sunk ever lower, savoring the almost palpable sense at Mrs. Clinton’s rallies that Americans will miss him when he is gone.