(AP) Democratic Sen. Tim Johnson was in critical condition recovering from emergency brain surgery Thursday, creating political drama over whether his illness could cost Democrats newly won control of the Senate.
The South Dakota senator, 59, suffered from bleeding in the brain caused by a congenital malformation, the U.S. Capitol physician said. He described the surgery as successful.
The condition, usually present at birth, causes tangled blood vessels that can burst unexpectedly later in life.
Democrats hold a fragile 51-49 margin in the new Senate that convenes Jan. 4. If Johnson leaves the Senate, the Republican governor of South Dakota could appoint a Republican to fill the remaining two years of Johnson's term - keeping the Senate in GOP hands with Vice President Dick Cheney's tie-breaking power.
Incoming Senate Majority Leader Harry Reid visited Johnson in the hospital Thursday morning and said afterward he was confident the senator would recover fully.
Asked about whether Democratic control of the Senate might be jeopardized, Reid said, "There isn't a thing that's changed."
Reid refused to comment on Johnson's medical condition, declining to even answer a question on whether the senator was conscious. "To me he looked very good," Reid said.
Johnson was taken to the hospital on Wednesday after becoming disoriented during a conference phone call with reporters. At first, he answered questions normally but then began to stutter. He paused, then continued stammering before appearing to recover and ending the call.
"The senator is recovering without complication," said Adm. John Eisold, the Capitol physician. "It is premature to determine whether further surgery will be required or to assess any long-term prognosis."
Eisold said doctors stopped bleeding in Johnson's brain and drained the blood that had accumulated there.
Johnson's condition, also known as AVM, or arteriovenous malformation, causes arteries and veins to grow abnormally large and become tangled.
The condition is believed to affect about 300,000 Americans, according to the National Institute of Neurological Disorders and Stroke. The institute's Web site said only about 12 percent of the people with the condition experience symptoms, ranging in severity. It kills about 3,000 people a year.
The senator's wife, Barbara Johnson, said the family "is encouraged and optimistic."
In a statement from Johnson's office Thursday, she said her family was "grateful for the prayers and good wishes of friends, supporters and South Dakotans."
A person familiar with Johnson's situation said surgery began late Wednesday night and ended around 12:30 a.m. Thursday and that the next 24 to 48 hours would be critical in determining Johnson's condition. The person spoke on condition of anonymity out of respect for the senator's family.
If Johnson were forced to relinquish his seat, a replacement would be named by South Dakota's GOP Gov. Mike Rounds.
A Republican appointee would create a 50-50 tie, and allow the GOP to retain Senate control.
However, Senate historian Don Ritchie said senators serve out their terms unless they resign or die. Nine senators have remained in the Senate even though illnesses kept them away from the chamber for six months or more.
Rounds' press secretary, Mark Johnston, said Thursday the governor had nothing new to say. "We're watching as much as everyone else," he said.
The governor, elected to a second four-year term last month, has been widely seen as the Republican candidate with the best chance to challenge Johnson in two years.
Other than Rounds himself, top possibilities if a replacement senator were needed include Lt. Gov. Dennis Daugaard and state Public Utilities Commission Chairman Dusty Johnson, considered a rising star in the Republican Party. Retiring GOP legislative leaders, such as state House Speaker Matthew Michels and Senate Majority Leader Eric Bogue, also might be considered.
Johnson, who turns 60 later this month, was admitted to George Washington University hospital at midday after experiencing what his office initially said was a possible stroke.
His spokeswoman, Julianne Fisher, later told reporters that it had been determined that the senator had suffered neither a stroke nor a heart attack.
Fisher said that after making the conference call with reporters from the recording studio in the basement of the Capitol, he then walked back to his office but appeared to not be feeling well. The Capitol physician came to his office and examined him, and it was decided he should go to the hospital.
He was taken to the hospital by ambulance around noon, Fisher said. "It was caught very early," she said.
A brain specialist not involved with Johnson's care said there's no way to know until Johnson is awake and able to answer questions how much lingering damage, if any, the bleeding may have caused. Still, while he'll remain in intensive care for a while, "he has every chance of recovery," said Dr. William Bank, who treats AVM and other neurovascular disorders at Washington Hospital Center.
Johnson is up for re-election in 2008.
In 1969, another South Dakota senator, Karl Mundt, a Republican, suffered a stroke while in office. Mundt continued to serve until the end of his term in January 1973, although he was unable to attend Senate sessions and was stripped of his committee assignments by the Senate Republican Conference in 1972.
Johnson, who was elected in 1996, holds the same seat previously held by Mundt.
South Dakota Secretary of State Chris Nelson said there were no special restrictions on an appointment by the governor and a replacement would not have to be from the same political party.
The Senate last convened with a perfect balance of 50 Republicans and 50 Democrats in January 2001. Then, the two parties struck a power-sharing agreement that gave control of the Senate to Republicans but gave Democrats equal representation on committees.
That arrangement lasted only until June 2001, when Vermont Republican James Jeffords became an independent who chose to vote with Democrats on organizational matters, giving Democrats control until Republicans won back the Senate in the 2002 midterm elections.
Johnson, a centrist Democrat, was first elected to the Senate in 1996 after serving 10 years in the House. He narrowly defeated Republican John Thune in his 2002 re-election bid. Thune defeated Sen. Tom Daschle, the former Senate Democratic leader, two years later.
Johnson is in line to become chairman of the Senate Ethics Committee.
He underwent prostate cancer treatment in 2004, and subsequent tests have shown him to be clear of the disease.
Johnson is the second senator to become ill after the Nov. 7 election. Wyoming Sen. Craig Thomas, a Republican, was diagnosed with leukemia on Election Day. He is back at work.