Stacy Garrity, Pennsylvania’s two-term elected state treasurer, said Monday that she will seek the Republican nomination to challenge Democratic Gov. Josh Shapiro ’s reelection bid, setting up what could be a contest between a low-profile officeholder and a potential White House contender in 2028.

State GOP leaders are expected to throw their support behind Garrity. Many of them are worried about a second run from state Sen. Doug Mastriano.

Republicans hope Ms. Garrity, the state treasurer, will give them a shot against Gov. Josh Shapiro. But he will be tough to beat, and the Republican field could still be complicated by Doug Mastriano.