Out of all the elected state offices, seems to me that it would be pretty unusual to go from state railroad commissioner to U.S. Senator, though I've seen stranger (like the IL Dems using "Recorder of Deeds" as a springboard to U.S. Senate and Secretary of State). Maybe Williams can use the U.S. Senate position to do some good things in the next six years and then run for Governor.
I can't believe Governor Good Hair is still there in 2009. When Bush first stepped down in 2000 and Perry took the reigns, I figured he'd be a seat warmer and hold the job for 2 years or so.
Disagree on appointing Williams to the seat prematurely. Voters tend to dislike that, having an unelected Senator representing them could cause a backlash when the seat is up for re-election.
It has happened just once before, in 1922 when Democrat Earle Mayfield made the jump (beating the 67-year old incumbent, Charles Culberson, who had held it since 1899). Unfortunately, Mayfield was also the Klan-backed candidate. He was promptly defeated in the 1928 primary by Congressman Tom Connally (Connie Mack's step-grandfather), who went on to hold the seat for the next quarter-century.