Romney backs challenger in Michigan
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Former presidential nominee Mitt RomneyWillard (Mitt) Mitt RomneyThis is how Republicans should shape message to win elections Maybe a Democratic mayor should be president Enforcing Trump's immigration plan will be harder than he thinks MORE (R) is endorsing businessman Dave TrottDavid Alan TrottGOP split on immigration is a crisis for Ryan’s team Pelosi: GOP discharge-petition holdouts helping Ryan ‘save face’ Two more Republicans back immigration discharge petition MORE (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.), the latest big-name Republican to weigh in on Trott's behalf.

"As someone who grew up in Michigan and has family currently living in the 11th District, I am confident that Dave Trott has the honesty, integrity and experience we need in Washington," Romney said in a statement released by Trott's campaign. "As a job-creator, Dave Trott knows how to balance budgets, cut spending, and fix the mess in Washington.  I am proud to endorse Dave Trott for Congress."

Trott has been pulling in huge sums for the race against Bentivolio, who won his seat after then-Rep. Thad McCotter (R-Mich.) failed to qualify for the ballot, and a write-in campaign organized by establishment Republicans fizzled against him.

Bentivolio's campaign is in shambles, and Trott is likely the favorite to win this primary.