This article neatly defines what it means to be a Republican. It also describes some of the methods by which the orthodoxy is enforced. Curiously, the orthodoxy is not defined and enforced exclusively by politicians. It is done by lobbyists like the National Rifle Association, and by "intellectuals" who work for conservative media and "think tanks". For example, Republicans are so intimidated by the gun lobbies that they voted against a bill that would have prevented the sale of guns to individuals on the FBI's watch list. The orthodoxy list is not complete, but it can be neatly divided into social values, which dominate the list, and policy issues on such things as global warming and tax policy. All Republicans oppose progressive taxes, and many favor reducing taxes in order to shrink government. They see no contradiction between cutting taxes and reducing budget deficits. They have also made significant cuts to the IRS budget. Reductions in the IRS budget have prevented it from enforcing compliance to existing tax laws. Tax evasion has cost the government more that it saved by cutting the IRS budget.
Of course there are some orthodoxies that define the Democratic Party. Most of them are more publically spirited than those in the GOP. Moreover, they are less consistently adhered to by Democrats. As someone once said "Herding Democrats is like herding cats." However, both political parties have to fund their election campaigns. As campaigns become more costly, they are even more dependent upon wealthy contributors. Working class Americans have not been well served by either party. The GOP has used social values as wedge issue to recruit white working class voters as they promote policies which are economically harmful. Robert Reich claims that Democrats cling to the belief that they will continue to be supported by upper middle class professionals who are swing voters in most elections.