WEST VALLEY CITY, Utah — Mitt Romney threatening to shut down the government is probably not what Republicans in Washington were expecting from one of the leading establishment figures of their party over the past two decades.

The 71-year-old, former presidential nominee is vowing to do whatever it takes to end profligate federal spending and the trillions in debt required to finance it, as he campaigns across Utah for an open U.S. Senate seat. If blocking another $1.3 trillion omnibus isn’t mission impossible enough, Romney wants to pick up the pieces of last year’s embarrassing Obamacare-repeal collapse.