Greg Pence ran for the congressional seat his brother, Vice President Mike Pence, once held.

INDIANAPOLIS — Greg Pence, the oldest brother of Vice President Mike Pence, won the Republican primary on Tuesday for the Indiana House seat once held by his more famous sibling, successfully leveraging his family name into prodigious fund-raising and ample votes that make him a heavy favorite to win the seat in November.

In his first run for public office, Mr. Pence, 61, ran a largely hermetic race, declining to debate his opponents and refusing most requests for interviews. Instead he made the rounds of Lincoln Day dinners and met quietly with voters in a district that stretches from Muncie to the north to the Ohio River to the south.

“I’m ready to serve again,” Mr. Pence, who enlisted in the Marines after college, said to a cheering crowd in his hometown, Columbus.

His closest challenger was Jonathan Lamb, who owns several small businesses and was…