The Constitution does not grant a sitting President immunity from civil litigation
because
score: -3
immunity for public servants is based on making sure officials aren't scared to do their jobs. Meaning if they do something within the confines of their official duty they shouldn't have to worry.
A designated office and the person in that office are two separate things. When a president functions within his executive duty it is legal outside of that their actions can come into question.
Even if one obtains the presidency and argues there must be separation of powers the Supreme Court has already made it known that they are able to say if the actions taken by the president are lawful.
Even if civil litigation is allowed to impact the president the risk of it actually interfering with his or her duties is not a serious matter of concern
The lower courts will know if an action brought against the president is a serious matter or just someone trying to have a day in the light, publicity.