Despite the recent health scare involving Sen. Tim Johnson, D-S.D., the balance of power in the U.S. Senate is not one heart attack or car accident away from shifting 180 degrees, Capitol Hill observers contend.

Indeed, even if Sen. Johnson–recovering from surgery to stop bleeding in his brain–is unable to serve out his Senate term and is replaced by the state's Republican Governor Michael Rounds (a former insurance agent), leaving the Senate technically deadlocked at 50-50, the practical impact would be somewhat muted by Senate rules.

Although Republicans would take an effective majority using the vice president as a tie-breaker on the Senate floor, committees would remain in Democratic control. Once the committee chairs are officially set this month, those positions will be kept until the next Congress convenes in 2009.