Turning Point

Eileen McGinley always voted Sinn Fein. She also told her five children to vote for the republican political party because "we thought they were fighting for justice" in divided Northern Ireland. That belief died along with her 23-year-old son James, who was stabbed through the heart 17 months ago in Londonderry by a member of the Irish Republican Army.

In the past few weeks, McGinley has watched other republican communities experience the same disillusionment. The catalyst: the murder of Robert McCartney, a 33-year-old father of two, again by members of the I.R.A. He was killed with...