  The Supreme Court's federal preemption decisions are notoriously
unpredictable. Traditional left-right voting alignments break down in the face
of competing ideological pulls. The breakdown of predictable voting blocs
leaves the business interests most affected by federal preemption uncertain of
the scope of potential liability to injured third parties and unsure even of
whether state or federal law will be applied to future claims.
  This empirical analysis of the Court's decisions over the last fifteen years
sheds light on the Court's unique voting alignments in obstacle preemption
cases. A surprising anti-obstacle preemption coalition is forming as Justice
Thomas gradually positions himself alongside the Court's liberals to form a
five-justice voting bloc opposing obstacle preemption.
