In fact, the Freedom Forum, which champions the First Amendment and whose own endowment has shrunk since the recession, now says it cannot continue to support the Newseum at the same level. In 2015, the most recent year for which financial statements are available, the Forum provided $21.4 million, or more than a third of the museum’s budget. It also took in $7.5 million in admissions. Still, the museum ran up a $2 million deficit.

“We have not been successful in closing the gap,” Jan Neuharth, the chief executive officer of the Forum, said.

All of which has put the museum’s future in doubt.

Jeffrey Herbst, who served as the Newseum’s chief executive officer and president for two years, stepped down from his post at the end of August.

“We had different visions of how to address the Newseum’s financial challenges and at the end of the day, decided to separate amicably,” Mr. Herbst said in a phone interview. He declined to elaborate.

The museum has just begun an in-depth review to try to right the ship. Everything is on the table, museum officials say, including selling the building that houses the Newseum.