South Dakota Democratic Sen. Tim Johnson is in critical condition Thursday after undergoing surgery for stroke-like symptoms at George Washington University Hospital.
There was no word on the nature of the surgery, which lasted past midnight, but an official said George Washington University Hospital was preparing to announce that Johnson's condition was critical.
Johnson was admitted on Wednesday after wrapping up a conference call with reporters, in which he became disoriented and stuttered a response to a question. He appeared to recover, asking for any additional questions and then signed off.
According to a spokeswoman for the senator, Johnson did not suffer a stroke or heart attack. His office had said earlier it was a possible stroke.
But several hours after she spoke, Dr. John Eisold, the Capitol physician, called that into question with a statement of his own.
"Senator Tim Johnson was admitted to the George Washington University Hospital today with the symptoms of a stroke. He is currently under the care of physicians at the George Washington University Hospital," Eisold said.
Johnson spokeswoman Julianne Fisher said Johnson was taken to the hospital around noon after walking to his Capitol office following the conference call. The Capitol physician came to his office and examined him, and it decided he needed to go to the hospital.
"It was caught very early," she said.
Johnson, who turns 60 on Dec. 28, is already a cancer survivor, having had his prostate gland removed in March 2004. According to news reports, he is also deaf in his left ear as a result of surgery to remove a benign tumor from his eardrum after returning from the Vietnam War.
While the extent of his illness isn't known yet, Washington political watchers are already noting that a Johnson replacement in the Senate would be made by Republican Gov. Michael Rounds.
South Dakota Secretary of State Chris Nelson said no special restrictions are put on such an appointment and a replacement does not have to be in the same political party. But Nelson added that the law applies differently for a senator than a representative.
"If there is a vacancy, the governor appoints a replacement and that person serves until the next general election," Nelson said. The next general election would be 2008. The governor would only call for a special election in the event that a congressman died, Nelson said.
With the 110th Congress split 49 Democrats, 49 Republicans and two independents that align themselves with the Democrats, majority control of the Senate could shift in the event Johnson is incapacitated. One former lawmaker chastised the political playmakers in town for discussing such options so quickly after Johnson was hospitalized.
"This is a pretty mean town and lets just keep him in our prayers," said former House Majority Leader Tom DeLay, R-Texas. "This town is so eat up with power that everybody, you know, that's all they think about. You go to ask somebody for a cup of coffee, they question why you asked, there must be an ulterior motive to you asking.
"Senator Johnson is a really nice man from strong South Dakota stock so I am sure he'll be all right," DeLay added.
The White House also issued a statement wishing the senator a speedy recovery.
"The President and First Lady have Senator Johnson and his family in their thoughts and prayers and they wish him a full and speedy recovery," said spokeswoman Dana Perino.
Sen. Harry Reid, D-Nev., the incoming majority leader, visited Johnson at the hospital after learning about the senator's condition around 1 p.m. EST. Reid suffered a mild stroke-like event in August 2005. He was not hospitalized and was diagnosed with having had a transient ischemic attack —- a brief interruption in the blood supply to a part of the brain. It can be a sign that someone's at risk later in life for a stroke.
"This is a very serious situation," a Reid spokesman said.
Johnson was first elected to the Senate in 1996, and defeated John Thune in his 2002 re-election by 524 votes. Thune then joined him in the Senate after defeating former Sen. Tom Daschle in 2004.
Johnson served in the House for 10 years prior to that, focusing his attention toward the committees on Indian affairs and energy and natural resources as well as appropriations. The latter allows him to direct funds to South Dakota.
Johnson has worked as a lawyer and county prosecutor and served several years in the 1970s and 1980s in the South Dakota state Legislature.
FOX News' Trish Turner and The Associated Press contributed to this report.