Presidential Involvement in State Politics

The Washington Post reports that President Obama has inserted himself into the Wisconsin state budget battle.  He criticized the provisions that would hamper state public employee unions and, according to the Post, “the president’s political machine worked in close coordination Thursday with state and national union officials to get thousands of protesters to gather in Madison and to plan similar demonstrations in other state capitals.”

Setting aside the merits of this particular dispute, as someone who is interested in how federal action can influence state policy choices, I am curious whether there is much recent precedent for Presidential involvement in state-level policy debates of this sort and, if so, whether it has had much effect.

Note: Please try and confine comments to the broader question of presidential involvement in state politics, not the debate over public-sector unions or the Wisconsin budget. If you want to comment on public sector unions, you may do that elsewhere.

UPDATE: Some of the comments raise immigration policy as an example, particularly this Administration’s criticism of Arizona’s immigration laws.  I am not sure this is an equivalent case, as there is a clear federal interest in immigration that is absent in the Wisconsin case.  The Constitution delegates control over immigration policy to Congress and there are serious preemption issues that arose in the context of Arizona’s immigration laws that are not present here.  Another possible example would be gay marriage, specifically the Bush Administration’s encouragement of anti-same-sex marriage initiatives at the state-level.