Sen. Johnson underwent emergency brain surgery overnight after falling ill at the Capitol. His illness brings into question control of the Senate in the next Congress because Democrats have only a one-vote majority in the Senate. If he is incapacitated or otherwise unable to serve, a successor would be chosen by the Republican governor of South Dakota, insurance agent Michael Rounds.

That would create a 50-50 tie, giving Vice President Dick Cheney the authority to potentially keep Republicans in control of the Senate.

Sen. Johnson, 59, was taken to George Washington University Hospital at noon yesterday, shortly after becoming disoriented during a conference call with news reporters. He underwent "a comprehensive evaluation by the stroke team," his office said. Aides later said he had not suffered a stroke or heart attack.

Sen. Johnson was co-author of legislation introduced in the last Congress that would create an optional federal charter for insurers, and has indicated to the industry that he would reintroduce such legislation in the new 110th Congress.

Gov. Rounds, however, while publicly stating he is not a candidate, is being pushed by the Independent Insurance Agents and Brokers of America, amongst others, to challenge Sen. Johnson for re-election in 2008, presumably because he would not support an OFC, which the IIABA opposes.

Gov. Rounds also opposed the Council of Insurance Agents and Brokers' legal efforts to break countersignature laws, testifying in federal court against the CIAB legal initiative last year. The state's countersignature law was later ruled by a judge to be unconstitutional.

Sen. Johnson was expected to head the Senate Banking Committee's key Financial Institutions Subcommittee, succeeding Robert Bennett, R-Utah. This is the Banking panel committee that deals with all regulatory, accounting and legal issues involving financial institutions.

If Sen. Johnson is unable to serve, Sen. Richard Shelby, R-Ala., who opposes an extension of TRIA, most likely would remain in control of the panel. But that is unclear.

In an analysis late yesterday of the implication of a 50-50 tie, Joe Lieber of Washington Analysis said that more than Vice President Cheney's ability to break ties, the real difference in the make-up of the Senate under a 50-50 scenario would be "in how committees are structured and the impact that might have on moving legislation--it obviously would be more difficult."

Citing the last time it occurred, in 2001, Mr. Lieber said that Sen. Trent Lott, R-Miss., was named majority leader since a Republican was the vice president at the time, giving the GOP nominal control; Republicans maintained their status as chairmen of the committees; an equal number of Republicans and Democrats were represented on all committees; and committee budgets for both the majority and minority were equally divided.

The agreement gave the power to the majority or minority leader to discharge legislation or nominations that had not been reported out of committee because of tie votes. Also, motions to cut off debate on any amendable item were prohibited during the first 12 hours of consideration--thus making it easier, Mr. Lieber said, to filibuster legislation.

"If a 50-50 tie occurs, the parameters for organizing the Senate this time around could be different, but we suspect they will fall along these lines," Mr. Lieber said.