The Republican presidential candidates are on a run of being combative with each other, which always holds out the opportunity for throwing some issues into sharp relief, but hasn’t yet done so. Senator Thompson seemed to aim at Mayor Giuliani and Governor Romney by saying, “Some think the way to beat the Democrats in November is to be more like them. I could not disagree more. … I believe that conservatives beat liberals only when we challenge their outdated positions, not embrace them. This is not a time for philosophical flexibility, it is a time to stand up for what we believe in.”

Mr. Romney, in turn, was aiming at Mayor Giuliani and Senator McCain. The former Massachusetts Governor said, “Conservatives that have heard me time and again recognize that I do speak for the Republican wing of the Republican Party.” This was an act of political grave-robbing, given that the line was lifted from a former governor of Virginia, James Gilmore, who ended his campaign not too long ago and used to deploy the line regularly against the rest of the Republican field — including Mr. Romney.

What would be helpful, in addition to the sparring, would be some specifics about what it is “we believe in,” what it is that the Republican Party stands for. Some suggestions:

• Reductions in top marginal tax rates provide incentives for growth and lead to greater government revenues in the long run. That is not always the case. There is a point on the Laffer Curve at which tax cuts on the top margin stop generating increased income, but we are nowhere near that point now. This is neither a Republican nor a Democratic principle — it was understood by Presidents Reagan, Kennedy, and Coolidge. It’s classical economics. But with the long Bush economic expansion showing some signs of coming to an end, it is a moment to advance this idea with urgency.

• Growth requires the free movement of goods, capital, and labor. This principle is going to be tested in the coming campaign as the Democrats flirt with protectionism on trade and the Republicans flirt with protectionism on labor. It was one of Reagan’s greatest achievements that he moved the Republican Party into the pro-immigration camp, and one of President Clinton’s greatest that he moved the Democratic Party into the free-trade camp. Both achievements are now in danger of being eroded – and could have seriously adverse consequences for the economy.

• America is a big tent. This concerns not only the immigration issue but cultural issues as well. America will be healthier, and both political parties will be healthier, if both parties are places where religious and secular Americans, blacks, Hispanics, women, gays, rich, poor, labor and management, farmers and city-dwellers, young and old, are welcome and comfortable. America’s diversity is one of its strengths. This is a principle Reagan understood, and he won by making the GOP itself a big tent.

• Projection of American military might leads to peace, and we need to be committed to winning our wars. Reagan understood that the Soviet Union was not only evil but a bizarre and temporary phenomenon. President Bush has emphasized that freedom is God’s gift to all mankind. We are at a juncture today when there will be temptations to isolationism, a tendency that infected both the pre-Eisenhower Republican Party and the post-McGovern Democratic Party. America will be safer and the world will be freer if the temptation is resisted. The GOP has held the high ground on this issue in the past generation and Republicans will lose it at their peril.

• Empowering individuals to make their own choices on education, health care, and retirement planning is a winning formula. Parents are the best at choosing a school for their child. Patients are best at choosing a doctor or a hospital or an insurance company. Individuals are best at deciding how to invest their own retirement savings. Against a Democratic Party dominated by the teachers’ union, pushing socialized medicine, and fear-mongering about Social Security privatization, these are winning issues for Republicans. Put them together with the tax issue — voters are taxed to pay for failing monopoly government-run school systems, and Democrats will push tax increases to pay for Medicare and Social Security — and they are even stronger.

We’d like to think the Republican primary battle — and the general election – will wind up being more about these issues than about who is the most pure and loyal partisan of the party. For all the pessimism with which the party’s membership is afflicted these days, an issues-based campaign offers the potential, the hope, of an optimistic vision for the country, one based not only on attacking the other candidates, Republicans or Democrats, but with the chance to make our great country even better.