Is this possible, now they can replace him without an election with anyone they choose, as long as it's the same party?
PA voting at it's finest. Like Flapp said, this was all know b4 the election. Guy had to read replies from a screen because he could not think for himself due to his brain injury. What could go wrong...
The state can require a special election (some states require a certain number of days remaining in the term prior to the next general election), or the governor can appoint a replacement.
However the vacancy gets filled, it's only temporary until another election is held for that seat.
Specifically, Pennsylvania follows the same process as 36 other states in that the governor does indeed appoint a temporary replacement:
In 37 states (listed below), U.S. Senate vacancies are temporarily filled by
gubernatorial appointment. The appointee serves until the next statewide
general election is held; the winner in that election serves out the remainder
of the term.
Since the next general election would be in 2024, any replacement this year would serve for the year 2024 plus the number of months remaining in 2023 at the time they are appointed.
Hawaii is one of 6 states that is bound by law to choose a replacement from the same party as the prior Senator. PA is not one of those, so theoretically, the Governor could appoint a Republican or any other person regardless of party affiliation.
The PA Governor is a Democrat, so it's unlikely to be anything other than a Dim in that seat.
https://ballotpedia.org/Filling_vacancies_in_the_U.S._Senate