The Washington Post’s columnist Richard Cohen laments that candidates are under heavy pressure to tailor their beliefs (or rhetoric) to “get past ideological bottlenecks” in early primary states: “For Republicans, it’s the religious right; for Democrats, it’s economic pressure groups such as teachers unions. The rest of us can only stand by, helpless, waiting for extremists to pick a man or woman on the basis of issues that mean less to us.”

To appeal to affluent trial lawyers, movie producers and union bosses, Democrats are expected to preach and moralize about “the inequality crisis.” This involves chanting about things that are flatly untrue, such as wage stagnation and the shrinking middle class, and speaking ominously of some undefined “economic anxiety.” New York Times columnist David Brooks noted “the Democratic view of the global economy has grown unremittingly grim. When John Edwards talks about the economy, you think he’s running for the Democratic nomination in 1932.”

A contest for the Democratic Party’s soul seems to be developing between super‐​grim “neopopulists” at the Economic Policy Institute, semi‐​grim “mainstreamers” at the Brookings Institution and the relatively upbeat “progressive realists” at Third Way. A new Third Way report, “The New Rules Economy,” notes that median household income is misleading because “one‐​third of American households are headed by someone who is either very young and earning an entry‐​level paycheck or by someone who is of retirement age and likely to be earning no paycheck.”

The authors suggest “the ‘real’ middle class is made up of households in their prime working years, ages 25 to 59, 75 percent of whom are couples and 56 percent of whom are couples with two earners. The median income of these prime‐​age households is more than $61,000. If it is a married‐​couple household, the median is more than $72,000. And if both spouses work, the median is more than $81,000.… The bottom line is that the middle class is shrinking, but not because the bottom is dropping out; it is because more people are better off. From 1979 to 2005, the percentage of prime‐​age households earning over $100,000 in current dollars grew 12.7 percentage points, while those earning between $30,000 and $75,000 shrank 13.3 percentage points.”

I made similar factual observations in the second and third chapters of “Income and Wealth.” Yet it seems far likelier that some wise Democratic presidential candidate might actually look at such facts if they came from progressives. Doing so requires abandoning the AFL-CIO party line and campaign support, of course. But a dose of independence and economic optimism could prove surprisingly effective in the general election.

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 same‐​sex “marriage” is not a federal issue, either. The federal government cannot prohibit stem cell research all over 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 a substantial majority of Republican voters approve of Mr. 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.