Gov. Brian Kemp of Georgia on Wednesday appointed Kelly Loeffler, a politically untested business executive, to fill a soon-to-be-vacated United States Senate seat in the state. The move put the governor at odds with President Trump, who had lobbied for a different candidate.

“We took an unconventional approach” to picking Ms. Loeffler, Mr. Kemp said in announcing the appointment, adding that he was “excited” to appoint a lifelong Republican “who shares our conservative values.”

The choice, which was expected this week, set off alarm bells among the president’s allies and was seen by political observers as an attempt by Mr. Kemp to shore up support from suburban Republican women.

The Senate seat is being vacated at the end of the year by Johnny Isakson, a Republican who is experiencing health problems.