If you want to persuade someone who disagrees with you politically, your best strategy is to appeal to their moral values and keep quiet about your own.
In a new study published in the Personality and Social Psychology Bulletin, social scientists from Stanford and the University of Toronto found that many political conversations work at cross purposes as each participant focuses only on his or her own value system. "Our natural tendency is to make political arguments in terms of our own morality," says co-author Matthew Feinberg. "But the most effective arguments are based on the values of whomever you are trying to persuade."
So, for example, telling conservatives that gay couples were patriotic Americans made them more likely to support legal same-sex marriage. Meanwhile, liberals could be convinced to look more fondly on big military budgets if they were told that military jobs were a great way to reduce economic inequality.