Rachel Maddow had a big scoop, and she handled it her way.

With a single tweet on Tuesday, Ms. Maddow, the MSNBC anchor, set the political world ablaze, announcing at 7:36 p.m. that she was poised to reveal previously unseen tax records from President Trump on her 9 p.m. program. (“Seriously,” Ms. Maddow added.)

In the need-it-this-instant world of online news, 84 minutes struck some journalists as an awfully long time to wait. The White House took advantage, releasing a pre-emptive statement that detailed Mr. Trump’s tax figures from 2005 before MSNBC had a chance to air its own report. The Daily Beast and other news outlets ran items as well.

Ms. Maddow, who is enjoying the biggest viewership of her show’s nine-year run, did not appear to mind. She opened her program on Tuesday as she usually does: with a deliberately paced, fact-heavy monologue, in this case reviewing Mr. Trump’s past refusal to release his taxes to catch up viewers on why this new revelation mattered.

The revelation itself, however, was held back until after the first commercial break, a windup that some fellow journalists, eager for any bombshells, found exceedingly lengthy.