The war in Iraq may be the lasting legacy of the presidency that is coming to a close, but the race between Sens. Barack Obama and John McCain could easily hinge on the stark differences in their approaches to the economy.

Economic issues have leaped past the war when pollsters ask voters for their concerns during this campaign, most recently last month in a survey for Pew Research Center for the People & the Press. Ninety-seven percent of the respondents said it was either very or somewhat important to them, ahead of the war, ahead of health care, ahead of immigration.

So how should those voters choose?

There are three main presidential levers on the economy, says Steven Schier, political science professor at Carleton College in Northfield, Minn.: taxes, spending and trade policy. McCain and Obama differ on all of them. Look for positions on “where to cut and increase taxes and spending and how much to regulate international trade,” Schier said in an email interview Monday.

Neither candidate takes a position far from his party’s traditional positions. In fact, McCain, in his major address on the economy in April, called for a return to the fiscal restraint philosophy long identified with Republicans, and he tends to rely on free markets as the best solution to economic problems.

Obama’s approach, in turn, was perhaps most vividly illustrated in his reaction to the housing crisis. He blamed deregulation of the financial industry and quickly offered a plan to help ailing borrowers. McCain, for his part, criticized plans to provide aid for homeowners struggling with their mortgages but then softened his position to let some delinquent borrowers who can prove they are creditworthy apply for new FHA loans.

Taxes

Front and center are the tax cuts pushed through Congress by President Bush in 2001 and 2003 to help the nation come out of a mild recession. Economists argue over whether they were effective or not, and they are set to expire in 2010.

Obama wants to repeal those cuts for people making more than $250,000 a year. He would, on the other hand, cut taxes for others, proposing a tax credit of $1,000 per family, which he says would eliminated federal income taxes for 10 million Americans. Obama dismissed calls this spring for a summer holiday from the federal gas tax, considering it ineffective and counterproductive to the effort to shift energy use in the country.

Although he once opposed them, McCain would keep the Bush tax cuts in effect and cut the corporate income tax rate from 35 percent to 25 percent. He would eliminate the alternative minimum tax, whose burden falls mainly, he argues, on 25 million middle class Americans. And he would double the personal exemption on federal income taxes. McCain favored the summer gas tax break for motorists and wants to ban Internet taxes.

Spending

So, how to pay for tax cuts? With the economy at the edge of recession, both candidates have stressed taxpayer relief, as opposed to fiscal restraint.

Obama has tended to emphasize his approach to taxes over deficit reduction, although he blames the Bush tax cuts as irresponsibly adding to the national debt. The fiscal plan on Obama’s website proposes a variety of steps to cut spending waste, reform budget rules to require new programs to pay for themselves and trim Congressional earmark spending. He also has said closing tax loopholes would help offset his spending plans.

McCain likewise criticizes earmark spending and has called for a one-year pause in discretionary spending growth outside military programs to evaluate program effectiveness. He would make wealthy older people pay for Medicare drug coverage to ease pressure on that program.

Trade

McCain is a free trade advocate, arguing that globalization is unstoppable and an opportunity to American companies and workers. He supports the North American Free Trade Agreement, which makes it easier to move goods from one country to another. Not to approve pending trade agreements with Colombia and South Korea will hurt the U.S. relationships with those countries, he argues. McCain has criticized Obama as a tool for organized labor on this issue, but he has told unions he would favor re-training efforts to help those industries affected.

Obama, on the other hand, has cautioned against problems he says are caused by unfettered trade. “Fair trade” should be the watchword, he says, arguing that free trade agreements can have the effect of exporting labor and environmental problems and hurting American companies and workers. He wants to re-open talks over the North American Free Trade Agreement.