A caucus of District 24 precinct committeemen selected Miller as the GOP nominee Wednesday evening. Miller was chosen over Adam Love and Brent Pittman.
Miller will face Democrat Charles Bender, also of Avon, for the seat during the general election.
The need for the GOP to replace Lawson -- both in office and on the ballot -- came about after Gov. Mitch Daniels named her secretary of state in March.
Miller formerly worked in the governor's Office of Management and Budget.
In Putnam County, District 24 encompasses Russell, Franklin, Jacskon, Clinton, Monroe, Floyd, Madison and Marion townships as well as five precincts in Greencastle Township: Greencastle North, Limedale, First North, Second East and Second West.
The district also represents the majority of Hendricks County.