The U.S. Chamber of Commerce has officially endorsed businessman David Trott (R) in his primary against Rep. Kerry BentivolioKerry BentivolioIndiana Republican: Leaders duped me Reindeer farmer saves 'cromnibus' with yes vote High drama as .1T spending package advances by one vote MORE (R-Mich.).

"On behalf of the U.S. Chamber, I am proud to support Dave Trott for Congress," said U.S. Chamber National Political Director Rob Engstrom. "His experience as a job-creator will serve the constituents of the district well and demonstrates his commitment to policies that will produce sustained economic growth and help get our country back on track."

The move comes as no surprise — Chamber officials have talked about defeating Bentivolio for months, and the Michigan Chamber of Commerce endorsed Trott a month ago.

Bentivolio won his seat when former Rep. Thad McCotter (R-Mich.) failed to qualify for the ballot in the 2012 elections, leaving him as the only Republican on the ticket. Trott has outraised him by huge sums this year, and Bentivolio is in the middle of a court battle with his former campaign manager about whether the campaign failed to pay him the salary he's owed.