Men usually dont leave their wives for their mistress, but I think it probably depends on their reason for having a mistress. I think that if the man is just plain old horny and wants a mistress then he wont leave his wife, he just wants the thrill of having more than one woman regardless of whether he is married or not. If hes having severe marital porblems I think it would be more likely that he indeed would leave his wife. I had a boss who left his iwfe for his mistress but I guess the wife had all kinds of issues, like not mailing otu the bills and spending the money instead on gambling, etc.
My first husband cheated onme, which after we divorced left me with the philosophy of I"M not the married one he is, so who cares....also I used tosay "marriage is mind over matter, if he doesnt mind what does it matter". However I wasnt ever anybody's mistress, I ended up involved with a married man who "forgot" to mention his wife and I did leave a bar with a cop that I knew was married but we just ended up fooling around on his boat, he gave me some unbelievable sob story about how he thought his wife was cheating on him....but that had no influence on what happened with him, I did it because I had wanted to. Never talked to him again, so I think it jsut depends on the situation the man is in with his wife.