Salon has a good timeline of Romney's swinging positions on abortion.

1994: He was for it.

2001: He was against it.

2002: He was for it.

2004: He was against it.

Each time, his changed view conveniently corresponded to his new political situation.

Article:
http://www.salon.com/news/mitt_romney/index.html?story=/politics/war_room/2011/08/10/romney_abortion

It's a good link to save.