Pennsylvania Gov. Josh Shapiro is an electoral juggernaut in America's biggest swing state — and he's widely seen as a likely contender for president in 2028. But strategists in both parties question how tested he really is.

Shapiro's success — he's cruised to victory in multiple statewide races — has come with an asterisk: He hasn't faced a well-financed opponent in recent contests, leading some political insiders to see him as more of a wildcard than his resume suggests.

Why it matters: Shapiro's unfamiliarity with intense, bruising campaigns could become a liability in the 2028 Democratic primary, where if he was a top candidate, he'd be confronted with a barrage of attack ads, opposition research and rivals with deep pockets.

A plugged-in Democratic operative in Pennsylvania suggested that because of Shapiro's lack of being tested, "it is totally possible that he has an incredible glass jaw — and that he is the Scott Walker of 2028."

Walker was the swing-state Wisconsin governor who looked good on…