Pennsylvania governor Josh Shapiro is perhaps the top contender to be Kamala Harris’s running mate. But Shapiro would be an awful selection, with a history of alienating and antagonizing core party constituencies and caving to pressure on major issues.
Actually if you were intending to vote for Harris but Shapiro would make you vote third-party, a republican would heartily encourage you to do so for the same reason a Democrat will happily encourage a Trump voter that doesn’t like Vance to vote third-party.