well strictly speaking, all the cases are not just accused or on going. swiss cases, they have been convicted by swiss courts already.
on the issues, its nice little game , you get the special treatment before you get elected without that one wouldnt have been a elected anyway. but once you become president, you are immunised 
people with no moral will not be deterred. I dont think Zardari will be resigning. would anybody? after resigning he will loose all immunity and may be straight to jail again! he wouldnt be signing his own warrants!