Madison businessman and political newcomer Bob Stefanowski has won the Republican primary for Connecticut governor, defeating four fellow GOP contenders.

The 56-year-old former General Electric executive promoted his ability to turn around struggling companies and dubbed himself “Bob the Rebuilder” in his campaign advertisements.

Stefanowski was the second-biggest spender in the campaign primary, trailing only former Greenwich hedge fund manager David Stemerman

Stemerman and former Trumbull First Selectman Tim Herbst questioned Stefanowski’s Republican pedigree, noting he became a Democrat only to switch back to the GOP shortly before announcing his candidacy for governor.

Stefanowski was the first to launch a major TV ad campaign in the race. He has called for eliminating the personal income tax.

Democratic Gov. Dannel P. Malloy is not seeking a third term.