Republicans actually used to be a more rational party, but not so today.
President Lincoln was an excellent example of how a Republican should conduct himself, but things went downhill after about the President Eisenhower era for Republicans.
I think the Republican party really went bad when it decided to allow the radical Tea Party to set the agenda and the limits of debate.
. . . The Tea Party is like the Taliban of politics. Radical extremism at the expense of the welfare of the country.