Yes. He’s the one. He claimed it was because Bush and Karl Rove supported John Sununu in the primary in New Hampshire in 2002.
He left the GOP in a specifically-timed blasting rant on the floor of the Senate that was able to be broadcast LIVE, not only by the 24-hour networks but the big three, I recall the smirking face of Dan Rather afterward. Then when Smith discovered he was going to lose his chairman’s seat, all seniority on his other committee assignments, then he did the BobSmithTwoStep, made some silly apology and asked back into the party, “Gee fellas, I’m sorry — let me remove my knife.”