For Republican candidates, the toughest litmus tests are not about any actual policy alternatives, foreign or domestic, but about "social issues." What most social issues have in common is that they are none of the federal government's business, let alone the president's.
The federal government will never pass a law banning or permitting abortion, so a presidential candidate's opinion on that subject has no practical relevance. Some hope the Supreme Court judges might limit Roe v. Wade, and thus return some authority to the states, but the next president is unlikely to have many chances to change this relatively young court.
The federal government will never pass a law banning or prohibiting states and religious organizations from defining marriage, and presidents cannot enact constitutional amendments, so gay marriage is not a federal issue, either. The federal government cannot prohibit stem cell research from occurring somewhere in the world, and the Feds are unlikely to meddle in private or state efforts to either discourage or support such research. Licensing of handguns is mainly a local issue, and no candidate is about to push for ending the federal ban on machine guns and assault rifles.
Although such nonfederal issues have virtually nothing to do with anything a president can do, Republican candidates are nonetheless expected to echo certain phrases to appease certain factions. Pundits imagine that failure to toe the mark on every one of these hot-button issues could be troublesome for John McCain and even more so for Rudy Giuliani. Yet polls show that a substantial majority of Republican voters approve of Giuliani's positions on all social issues, so the demand for ideological purity in these cases seems to require that candidates capitulate to a minority of the minority party. That does not sound like a recipe for success.
Reporters compiling lists of where candidates stand on the issues could simplify the process by asking where candidates stand on issues in which a presidential decision might actually be involved -- such as avoiding wars, establishing a workable immigration policy or restraining runaway federal spending. Unless we see some gutsy political entrepreneurship, for a change, gloomy economic themes may continue to dominate Democratic primaries and social issues may dominate Republicans primaries.
In the general election, however, the winner will emphasize concrete ideas about those issues a president can actually affect and be properly optimistic about the wondrous U.S. economy.