As members of the U.S. Senate argued over the rules for President Trump’s impeachment trial Tuesday — a day so historic that one senator fell asleep — one little-known guideline started to make the rounds on social media, leaving more than a few outsiders to wonder whether the entire chamber is in the pocket of Big Dairy. Or Elsie the Cow.

The rule came to light on (where else?) Twitter, when reporter Matt Laslo milked his sources for this random bit of Senate esoterica:

Just like the Korova milkbar in “A Clockwork Orange,” this cold glass of Senate regulations got everyone ready for a bit of the old ultraviolence.

But before America, collectively, has a cow, let’s cool down, have a long pull of 2 percent and take a deep look at the Senate rules. The allowance of milk on the chamber floor may not be what it seems.

I called up Betty K. Koed, the Senate historian, and she poured some cold milk on all this reporting about what senators are allowed to drink in the chamber. She photocopied and emailed me the “Rules for Regulation of the Senate Wing of the United States Capitol and Senate Office Buildings.” It’s part of the official Senate manual, and it’ll induce drowsiness faster than a warm glass of milk before bedtime. But nowhere in the regulations is there a mention of milk (though there’s no mention of candy either, yet that hasn’t stopped the tradition of the candy desk).

But on page 758 of “Riddick’s Senate Procedure: Precedents and Practices” — described as the “nearest thing to the Bible that the Senate has,” by Washington Post colleague Felicia Sonmez — the book clearly states, “Senate rules do not prohibit a Senator from sipping milk during his speech.” (They also do not prohibit a senator from leaning on a desk while speaking. Who knew?) There is a footnote next to the milk rule. It cites a Congressional Record from more than 50 years ago.

If you dig up the Congressional Record from Jan. 24, 1966, you’ll find a little-known chapter of Senate history in which the late Everett McKinley Dirksen (R-Ill.) bravely asked the presiding officer for a glass of milk. (I should perhaps note that Dirksen’s oratorical prowess earned him the title of the “Wizard of Ooze.”) Here’s the exchange, in a language so polite and decorous that it sounds like a clip from a Merchant Ivory film:

Dirksen: “Is it in violation of the Senate rules if the Senator from Illinois asks one of the page boys to go to the restaurant and bring him a glass of milk? If it is in violation of the rules, I will forget it.”

Presiding officer: “There is nothing in the rules to prohibit the Senator from requesting a glass of milk.”

Dirksen: “I thank the Chair, because water becomes pretty thin after a period of time. My lunch today will be a tall glass of milk.”

Yet if you examine this exchange closely, it seems clear there has been a misreading of the presiding officer’s response. He merely said, “There is nothing in the rules to prohibit the Senator from requesting a glass of milk.” (Emphasis mine.) Nowhere does the chair say that Dirksen is actually allowed a glass of milk (though you can perhaps assume Dirksen’s request was granted).

Regardless, even if Dirksen’s one-off wish became enshrined in Senate regulations, it would appear to be a rule that’s more of an in-joke, a wink and a nod to a rare moment of humor on the staid Senate floor. Because Koed, who has worked at the Senate Historical Office since 1998, has never seen anyone drink milk in the chamber in all her years.

“There is a case in the 1950s when we know Strom Thurmond used orange juice to help fuel him through his 24-hour filibuster,” Koed said about the late senator from South Carolina. “In recent years, it’s only been water, either still or sparkling, that’s allowed in the chamber.”

If a senator needs more than water during one of those late-night sessions or a marathon filibuster, he or she can sometimes duck into the Republican or Democratic cloakrooms for a drink or a bite, Koed said. The cloakroom staff, she added, will make sure senators do not bring anything into the chamber that’s against the rules.

“The Senate has always been very careful about its decorum and very careful about how senators act on the floor, how everything looks on the floor,” Koed said. “It’s become even more so since 1986, when C-SPAN began covering the Senate, because then they became even more aware of how things might look on television.”

The most famous milk-drinking moment in Senate history doesn’t even belong to Dirksen. It belongs to Robert M. La Follette. On May 29, 1908, as the Senate was preparing to adjourn for a long hiatus, La Follette, a freshman senator from Wisconsin, launched into a multi-hour filibuster as temperatures soared into the 90s inside the chamber. As he was holding forth, La Follette asked a page to get him a “turkey sandwich and a glass of milk fortified with eggs.” According to a Senate recollection of the incident, kitchen staffers, unhappy at working until the wee hours of the morning, may have allowed the senator’s eggnog to ferment a little too long on the counter.

Per the Senate’s own accounting:

The eggnog did not taste right. He took a larger sip and promptly thrust it aside. Soon, he experienced digestive difficulties. A subsequent analysis revealed that the mixture contained enough toxic bacteria to kill anyone consuming the entire glass. Tired, drenched in perspiration, and feeling increasingly ill, the iron-willed La Follette continued speaking until after 7 a.m., when a colleague arrived to relieve him.

La Follette, Koed added, almost died from the incident. Afterward, the Senate considered banning all beverages from the chamber.

The La Follette episode, by the way, is offered as a Senate history lesson. It is not a suggestion on how to deal with sparring senators during the impeachment trial of President Trump.

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