States have set it up and courts have agreed: your state of residence does not matter, the state where the money is earned is the deciding factor. Earnings at a CA tournament will be taxed by that state — same thing happens to NBA and NFL players who are paid by the game. The key legal word is “locus”. If you are a Rush Limbaugh fan, you may recall his issue with NY on being taxed there for days he broadcasts from the NYC studio. Thus, Rush’s “Southern Command” in south FL.
Lefty can just forego the CA tournaments if he wants to avoid those taxes.
Golfers like Woods and Mickelson make 80-90% of their earnings from endorsements. Mickelson made somewhere in the neighborhood of $4 million in tournaments and approx $45 million in endorsement deals. Same for Tiger — just different amounts. Before Tiger’s fall he was making nearly $90 million a year in endorsement income. Moving to Florida would save Mickelson millions on his off course earnings.