Former Representative Matt Gaetz, the Florida congressman-turned-attorney-general-nominee-turned-cable-news-host-with-baggage, made a bold proclamation at 9:46 a.m. on the opening day of the 119th Congress.

“Mike Johnson will be elected Speaker today,” Mr. Gaetz, who brought down the last Republican speaker, wrote on social media. “On the first vote. People might like or dislike that. I’m just reporting the news.”

With potential holdouts hinting at a revolt against Mr. Johnson, it seemed like an overly optimistic statement regarding the fate of an embattled leader presiding over a minuscule majority. But in the end, it turned out that Mr. Gaetz was well-sourced on the story.

Several hours and one prolonged roll-call vote later — after six abstainers finally said Mr. Johnson’s name and President-elect Donald J. Trump called in from his golf course in Florida to persuade two other defectors to switch their votes — Mr. Johnson won the gavel.

The relief was apparent on his anxious face.

It felt like an appropriately wobbly start to what promises to be a turbulent Republican-majority Congress at the dawn of Mr. Trump’s second term.