CLEVELAND — Corey Lewandowski, Donald J. Trump’s former campaign manager, was sitting in a bar here at sunset on Monday, staring out at the arena where the boss who fired him last month would soon accept the Republican nomination for president.

As he reflected on the past year, Mr. Lewandowski’s eyes began to well up.

“I got the reputation as a tough guy; that’s my reputation, right?” Mr. Lewandowski asked, a reference to his shiv-in-the-side tactics, which propelled Mr. Trump’s rise but also contributed to Mr. Lewandowski’s abrupt fall. Rival Trump advisers forced him out, calling him unfit to lead.

“The people who know me know that I care,” he said, as a tear trickled down his right cheek. “My heart,” he added, “is in the right place.”

This is not, to say the least, the Republican National Convention that Mr. Lewandowski had expected.