Conservatives today are in a funk. The strains of governing, the challenges of war, and the frustration of an unsuccessful mid-term election have contributed to unease and unhappiness. But deeper than these issues is an intellectual fatigue and uncertainty about where the attention of the conservative movement now should be directed.

What domestic issues can unite and motivate conservatives to great political exertions, and can win the allegiance of the public?

In this respect, the right is partially a victim of its own successes. If 25 years ago you had asked an American conservative to name the preeminent domestic policy challenges of the day, you probably would have gotten back, along with a general worry about cultural decline, some combination of welfare, taxes, and crime.

Few conservatives today would name any of these three as the foremost problems, and even on the cultural front they could point to some advances. This is due, in large part, to a series of conservative successes that have transformed American politics and made conservative theories of economics, law enforcement, and welfare the accepted wisdom. Success has not been complete in any of these areas, of course, but the struggle over first principles, over which way to go in general, has been won.

Today the left — which for decades fought vigorously on all three fronts — offers scant opposition on any of them. No leading Democrats are arguing that we undo conservative achievements on welfare and crime. And even on taxes, which liberals want to increase, no Democrats are arguing that we return to the days when the top rate of taxation was 70%.

But what now? On what issues can conservative principles point to popular reforms today? The most prominent domestic policy concerns of the day would seem, at first glance, to favor the left. Health care, income inequality, and the environment, among other issues, have long been identified with American liberals, and conservatives have been uncomfortable taking them up.

But the notion that the left owns these issues is not a fact inherent in the problems themselves; rather, it is a failure of conservative imagination. In fact, it is precisely these kinds of issues that should now be front and center on the conservative agenda, not only because the public cares about them, but also because the left is far more vulnerable on them than it seems. Conservatives should fight precisely on what is perceived to be liberal turf, as they have done successfully before.

Welfare reform — the most successful social policy innovation in generations — offers a powerful model. For decades welfare was the quintessential liberal issue, and while conservatives offered serious reasons for concern and opposition, they did not offer enough in the way of concrete reforms.

But when conservatives finally turned their attention to reforming the welfare system — applying basic conservative premises about the centrality of the family, the power of economic incentives, and the value of self reliance — they took control of the issue and eventually enacted a sweeping and dramatically successful reform. Democrats had been right to focus on welfare, but their approach was disastrous. Republicans were wrong to ignore it, but once they took it on and offered an alternative, they won.

Something of a similar dynamic now presents itself on a range of other issues. Health care, for instance, is the foremost liberal issue of the moment. Since conservatives have been absent from the argument, liberals have persuaded themselves that the public wants national government-funded, if not government-run, health care. By committing to this course, the left has actually made itself quite vulnerable.

The idea of a new and enormous government bureaucracy with deep reach into the life of every family is inherently disconcerting — and rightfully so, given the Canadian and much of the European experience. It threatens to add to, not diminish, the public’s health care anxieties.

An effort to describe the problem in its particulars and frame it in terms of the security and stability of families, the proper ordering of economic incentives, and the need for prudence in taking on a challenge of such scale would highlight the extremism of the Democrats’ proposed solution. It also would open the public to a set of reasonable reforms — to the tax system, to Medicaid, and to insurance regulation — that offer greater stability, lower costs, and better access to private coverage.

Health care today, like welfare 15 years ago, offers conservatives an opportunity both to correct gross inefficiencies and failures of public policy and to highlight the left’s instinct for statism and overreaching. Understood in terms of conservative first principles, it presents a great opportunity, not political quicksand.

If anything comes close to being as important as health care on the Democrats’ agenda, it is income inequality. It is the watchword of every prominent Democrat. Conservatives have wanted nothing to do with it. But here again, conservatives should seize an opportunity to make a case for their economic vision.

The debate over inequality must be transformed, as Arthur Brooks has argued, into a case for economic mobility. The problem with the gap between the rich and the poor, after all, is not that the rich are rich, but that the poor are poor. The solution, then, is not best understood through the prism of economic equality — a meaningless notion, good only for fanning envy and disillusion — but through the prism of economic mobility.

The key steps toward mobility have long been clear: school, work, and marriage. Conservatives know how to make that case and translate it into policy. They must do so, and again make clear the basic difference between their notion and the left’s notion of freedom and the role of government.

The environment, too, is carelessly taken to be a liberal issue these days. Again, conservatives have been terrified of touching it for too long. Here, too, they should be more assertive.

Once we acknowledge the fact that global temperatures are rising slightly and that human activity is among the causes, we are left to ask what should be done. Here, as in health care, the Democrats’ proposals are a gross overreach. It’s as if steep punitive taxation is the goal and climate change arguments are just a means to get there.

As chief executive officer of Applied Predictive Technologies, Jim Manzi, has written, global warming calls for investments in research for climate modeling, mitigating the effects of fossil fuels, and pursuing other sources of energy. Republicans, again, have an opportunity to provide constructive proposals to counter the reckless and excessive prescriptions of the left, and to plainly describe them as such.

In these areas and others, conservatives have ready-made opportunities to take the initiative and to make a case for reform aimed at advancing the interests of the American family. As in the past, they would do this best by returning to their guiding principles — the defense and promotion of virtue and liberty — and by applying them to the key issues of today.

They should take on the left where the left seems strongest and, as in the past, show how solutions that begin from conservative assumptions will better appeal to the American public, and will better address the country’s problems.

Messrs. Levin and Wehner are fellows at the Ethics and Public Policy Center.