Can anyone explain how this happens?

In what amounts to an epic constitutionality #fail, Senate Democrats may have blown their chances to see their food safety bill signed into law.

The U.S. constitution requires that any revenue-raising bill must originate in the House of Representatives. To honor this provision, the Senate often finds a discarded old House bill, strips it bare, and uses it as a "shell" and passes it back to the House.

They somehow forgot to do that this time.

....

According to Hoyer, this has happened multiple times this Congress, causing severe legislative angina.

TPM