I doubt such an announcement would have any effect. What would have an effect, tho I would expect it would only be leaked and not announced, would be if was revealed that Michelle had had an abortion. Not that I expect that to be the case.
I think an abortion might help the GOTV efforts for some pro-choice women. But it would be a huge scandal for the right-wing press; and could motivate the christian conservatives to vote. But for all the coverage that abortion gets in the liberal media, I think most average white Americans don't think about it much at all, or its very low on their list of concerns. Abortion is really only a priority issue for white women.
