Technically, the vice president serves as president of the Senate. But he doesn’t spend all day in that role, so senators from the majority party rotate the job of presiding.

The responsibility of the “presiding officer” is simply to maintain order and decorum over the Senate floor. Senators performing that duty don’t generally offer commentary on the proceedings.

So it raised a few eyebrows when, after the official prayer to open Senate business, Sen. Charles E. Grassley (R-Iowa) offered his own prayer from the dais.

“Let’s all pray that the president will have wisdom to sign the bill so government doesn’t shut down,” Grassley said.

Congress is on edge as President Trump has yet to fully commit to signing the deal to avert a government shutdown, though most expect he will. But Grassley’s comments are a not-so-subtle reminder that with Trump, anything can happen.

The Senate tends to be the stuffier of the two congressional chambers, so Grassley’s commentary both regarding Trump and the legislation at hand is significant.

“It is unusual for the presiding officer to make a statement like that,” said Ira Shapiro, a consultant and author of “Broken: Can the Senate Save Itself and the Country?” “Generally, senators play a more neutral role while sitting as presiding officer. Senator Grassley is notoriously and admirably independent and outspoken, and these are unusual times.”‘‘