A common sense rule, extremely unlikely to garner support in the Capitol pigsty, would be that no government resources, vehicles, aircraft or personnel may be used for any trip which includes political events of any kind. Normal Americans can recognize the simple, yet clear, moral imperative that their money should not be used for political fundraising or campaigning without their consent, such as the check-off box on the IRS-1040 (is it still there?). Politicking on the taxpayer dime also creates the outrageous advantage that goes with incumbency, which is why we have these jerks camped out in DC for 30, 40 years and more, enriching themselves, passing the pork around and growing every day less and less representative of the people who sent them there.
As I said, common sense will find no takers in the pigsty.
The President is the de facto head of a political party. To say they can't attend or participate in political events isn't realistic.