NEWARK, N.J. -

On the eve of the George Washington Bridge lane-closing trial involving two former allies of Republican Gov. Chris Christie, one defendant says the government is changing its theory of the case.

Bill Baroni says in a court filing prosecutors now claim his motive was to curry favor with Christie by causing traffic jams to punish a mayor who didn't endorse Christie's 2013 re-election.

Prosecutors say the question of motive matters less than the fact Baroni joined in the alleged scheme.

Baroni, a former top executive at the Port Authority of New York and New Jersey, and former Christie staffer Bridget Kelly are charged with fraud, civil rights and conspiracy charges. Opening statements are scheduled for Monday in Newark.

The most serious charge carries a maximum prison sentence of 20 years.