Robert Byrd, the Senate's oldest member, was rushed to the hospital today after a fall in his McLean, Va., home.

It's the latest in a string of health setbacks for Byrd, who is frankly—to judge by his public performances in recent months—too infirm to serve effectively in the Senate. But he and his staff have clearly made a decision to stay on until he's no longer physically capable of being a senator. He was hospitalized last February after a fall, and again in May after coming down with a staph infection.

Byrd's spokesman told Politico that the senator will not likely be admitted, and that his "caregiver" called 911 out of an abundance of caution after Byrd "stood up too fast" and fell down:

"Byrd apparently stood up too fast this morning in his home and fell down," said Jesse Jacobs, a spokesman for the senator. "To err on the side of caution his caregiver called an ambulance. He was taken to the hospital where he is currently being checked out. At this point in time there is no indication that he will be admitted."

Byrd's health issues are an obvious cause for concern for proponents of healthcare reform: He is a much-needed Democratic vote, and if he doesn't recover in time to make it to the Senate floor in time for the vote, his absence could jeopardize the whole project. If he dies or resigns, West Virginia's Democratic governor Joe Manchin would appoint a replacement.