Even before the release of his book, “A Higher Loyalty,” the White House, working in concert with the Republican National Committee, began an all-out campaign to besmirch “Lyin’ Comey” — the name of a website the party created to make the case — as dishonest, self-serving and driven by partisanship. But with his one-liners and cutting asides about the president, Mr. Comey only appeared to play into the hands of allies of Mr. Trump, who are eager to paint the former F.B.I. director as just another figure working for the president’s defeat.

And Mr. Comey has drawn bipartisan criticism with his latest efforts to explain — and, to some degree, recast — his much-criticized handling of the investigation into Hillary Clinton’s use of a private email server. Mark Mellman, a longtime Democratic pollster, said Mr. Comey’s standing had been undermined by the one-two punch of liberal attacks over his role in the 2016 election and the more recent assault led by Mr. Trump and his Republican allies.

“Trump has tried to define him as a bad operator, and the problem for Comey is that you can quote a lot of Democrats saying the same,” Mr. Mellman said.

At this point, it seems unlikely that Mr. Comey’s book or his performance in interviews to promote it will sway public opinion in a country that is already intensely polarized along partisan lines. Mr. Trump’s approval ratings have been similar for months, and the roughly 40 percent of Americans who support him have proven remarkably unshakable, while the 56 percent who disapprove will probably not change their views on Mr. Comey's account.

While Mr. Comey is sure to captivate the public for a few days with his biting descriptions of the president and dramatic of interactions with him, the combination of the supercharged news cycle and the looming — and far more consequential — investigation by Robert S. Mueller III, the special counsel probing Russia’s meddling in the 2016 election, is sure to eventually overshadow his memoir.

“It keeps the story of cover-ups and corruption on the public radar while Mueller is doing his investigation, but Comey is just a pit stop along the way of that,” said Stephanie Cutter, a veteran Democratic strategist. “Much to Comey’s chagrin, his moment has passed. There’s nothing in this book we don’t already know. He just adds one more hole to a ship that’s already sinking.”

Mr. Comey plainly considers himself to be a figure who is above the political fray, driven and guided solely by facts. His friends and advisers say he wants the book to stir a conversation about the value of honesty.