But Johnson may be best known for his son Brooks, an Army sergeant who has served in Afghanistan and Iraq, wars Johnson voted for. Before voting to authorize the use of force in Iraq, Johnson said that his son "gives me special empathy for the families of other American servicemen and women whose own sons and daughters may possibly also be sent to Iraq."
Beyond praying for a friend, Democrats may also be praying to keep their narrow 51-49 Senate majority.
If Johnson's Senate seat were to become vacant, South Dakota law would empower Republican Gov. Mike Rounds to appoint a replacement.
He would likely pick a fellow Republican, creating a 50-50 Senate with Vice President Cheney as the tie-breaker, leaving the GOP again in control of the Senate.
"By one person changing, the entire Senate changes, changes the president's agenda, changes the Senate's agenda," American University professor James Thurber said. "And that will change events for Iraq, taxes, energy."
Dismissing such talk as premature, Reid said yesterday that everything is still proceeding for his party to assume power.
"There isn't a thing that's changed. The Republicans selected their committees yesterday. We've completed ours," he said.
But Reid, who was with Johnson's family at the hospital Wednesday night and Thursday morning would not say whether Johnson is yet conscious.
"I'm not going to talk about his medical condition. I saw him -- he looked great," Reid said.
Members of the Senate Republican leadership have signaled they will not make an issue of Johnson's potentially prolonged absence from the Senate.
"Johnson can take all the time he needs," said one senior GOP aide. "He's family."
Another senior GOP leadership aide said the position of Senate Republicans is "status quo ante … We're doing the same things today we were doing last week. Nothing's changed."
Historically, senators have remained in office even if an ailment kept them bed-ridden for years. There is no Constitutional requirement for senators to show up to work, Senate historian Richard Baker said. "All that's required is age, residency and citizenship."
Questions about senators not serving their constituents would face the even tougher Constitutional challenge of "Who would decide when a senator was not performing?" Baker said.
"Who would determine whether they are cognizant?" he said. "Do we have a board of doctors that comes in? Is it Terri Schiavo all over again? The framers of the Constitution didn't go there."
Someone making that decision would "remove the sovereignty of the Senate and the independence of Senators," Baker said.
In 1943, the 85-year-old and ailing Sen. Carter Glass, D-Va., stopped coming to work.
As Time magazine reported at the time, the "Senate's cantankerous grand old man was too ill to go to Washington to take what may be his last oath. The Senate adopted a rare resolution and went out to him" at his Lynchburg, Va., home. Colonel Edwin A. Halsey, the Senate Secretary, administered the oath to Glass, who never showed up to work again and died three years later.
In November 1969, Sen. Karl Mundt, R-S.D., was stricken by a severe stroke but he served out the remainder of his term -- staying in office through January 1973. Mundt was stripped of his committee assignments but he remained in office, though "his responsibilities were shouldered by members of his staff," according to the Mundt Archives at Dakota State University.