Reagan memorial: Democrats need not attend?

I hear, via Ezra Klein, that Clinton and Carter will not be speaking at the Reagan memorial service. If there wasn't a clearer sign that this event is being used as a big fat commercial for the Republicans and their boy Bush then what more is needed?

Clinton and Carter both spoke at Nixon's funeral and each gave classy speeches. Do the Republicans assume that they will trash Reagan at the memorial?

I thought Reagan was supposed to be the American President. But, by these arrangements, they are saying that he is only a Republican President (unless you think only Republicans are real Americans in which case you wouldn't see the problem.)