If Kerry is excommunicated before Nov. 2 he will lose most of the ~48% of the Catholic vote he currently has, plus a few others.
Not a chance in the world that they will act before election day. So this won't have much impact on the race, but it may have a great deal of impact on the future ability of heretic Catholic politicians to run and hide from the consequences of their sins.
Are you sure? The Kerry camp's response would be something along the lines of: "This is just another right-wing smear campaign orchestrated by Karl Rove who is manipulating radical fundamentalist Bishops who took time out from their busy schedule of molesting young boys to write this scurrilous document...and we question the timing of this action."
The "Catholic vote" is the backbone of the abortion license in this country.
It sustains the twelve Catholic senators who are blocking the appointment of pro-life Federal judges.
Any attempt by the Church to condemn Kerry will help him, not hurt him.