Hamas in PA elections

Palestinian Authority President Mahmoud Abbas said in Tokyo recently that including Hamas in the election process may help to quell the violence in the Middle East. In Iraq, elections have not had the effect of lowering the level of violence. Are there differences in the situations of Iraq and Palestine/Israel that would let us hope that what has not worked in Iraq will work in Palestine?

Of course, excluding Hamas from the elections is likely to bring about even worse repercussions.