I can see The Punisher going after Lex Luthor, while he's a
candidate for presidency, but Superman would certainly not let
Frank Castle (Punisher) off Luthor whether he wins the presidency or not.
And of course, Batman will also be with Supes to stop Frank from
assassinating the sneaky ratbag as well.
In the end, Supes would convince Frank that he, Bats
and others will handle taking Luthor down, but they'll do
it the right way. And even if Luthor, they'll still continue
to turn the tide on Lex anyway they can.
Out of respect for Supes, Frank decides not to go through
killing Luthor and let him and others handle the ratbag.
This story is likely to happen in either a Superman comic book
or another comic book series.