The political press — and presumably the donors and activists who consume it — has handed Jeb Bush his walking papers. Another poor-to-middling debate performance last night in Colorado is the proximate cause.The debate left me unusually queasy, and I find the notion of Bush’s departure from the field even more unnerving. I consider Bush pretty smart, pretty honest and pretty competent. You won’t get me to defend his boneheaded and fully anticipated attack last night on Marco Rubio’s Senate absenteeism, however. I have limits.