John McCain is a maverick and Barack Obama is a postpartisan problem-solver. But you wouldn't know it by looking at their economic plans. Both candidates' proposals faithfully reflect the traditional economic priorities of their respective parties. That makes the track records of past Democratic and Republican administrations a very useful benchmark for assessing how the economy might perform under a President McCain or a President Obama. The bottom line: During the past 60 years, Democrats have presided over much less unemployment and much more robust income growth.

The $52.5 billion plan Senator McCain announced last week includes $36 billion in tax breaks for senior citizens withdrawing funds from retirement accounts and $10 billion for a reduction in the capital gains tax. Those are perks for investors, most of whom are relatively affluent. (McCain is also proposing a two-year suspension of taxes on unemployment benefits, but that's a fraction of the plan's cost.) He also favors broader tax cuts for businesses and wants to extend President Bush's massive tax cuts indefinitely, even for people earning more than $250,000 per year.

McCain's proposals reflect the traditional Republican emphasis on cutting taxes for businesses and wealthy people in hopes of stimulating investment – "trickle down" economics, as it came to be called during Ronald Reagan's administration. But will proposals of this sort really "stop and reverse the rise of unemployment" and "create millions of new jobs" as McCain has claimed? The historical record suggests not.

President Bush's multitrillion-dollar tax cuts, which were strongly tilted toward the rich, could not prevent (and may even have contributed to) significant job losses. On the other hand, when Bill Clinton raised taxes on affluent people to balance the federal budget (while significantly expanding the Earned Income Tax Credit for working poor people), unemployment declined substantially. Under Clinton's watch, 22 million jobs were created.

Prefer a broader historical comparison? In the past three decades, since the Organization of the Petroleum Exporting Countries oil price shocks of the mid-1970s and the Republican turn toward "supply side" economics, the average unemployment rate under Republican presidents has been 6.7 percent – substantially higher than the 5.5 percent average under Democratic presidents. (The official unemployment rate takes no account of people who have given up looking for work or taken substantial pay cuts to stay in the labor force.) Over an even broader time period, since the late 1940s, unemployment has averaged 4.8 percent under Democratic presidents but 6.3 percent – almost one-third higher – under Republican presidents.

Lower unemployment under Democratic presidents has contributed substantially to the real incomes of middle-class and working poor families. Job losses hurt everyone – not just those without work. In fact, every percentage point of unemployment has the effect of reducing middle-class income growth by about $300 per family per year. And the effects are long term, unlike the temporary boost in income from a stimulus check. Compounded over an eight-year period, a persistent one-point difference in unemployment is worth about $10,000 to a middle-class family. The dollar values are smaller for working poor families, but in relative terms their incomes are even more sensitive to unemployment. In contrast, income growth for affluent people is much more sensitive to inflation, which has been a perennial target of Republican economic policies.

Although McCain portrays Senator Obama as a "job killing" tax-and-spend liberal, the new $60 billion plan Obama unveiled last week also has a tax break as its centerpiece – a tax break specifically tailored to create jobs by offering employers a $3,000 tax credit for each new hire over the next two years. Obama's proposal would also extend unemployment benefits by 13 weeks for those who remain jobless, as well as match McCain's in suspending taxes on unemployment benefits.

Obama's new proposal complements $115 billion in economic stimulus measures he had already announced, including $65 billion in direct rebates to taxpayers and $50 billion to help states jump-start spending on infrastructure projects. All of this is squarely in the tradition of Democratic presidents since John F. Kennedy, who have relied on public spending and tax breaks for working people to stimulate consumption and employment during economic downturns.

These and other policies have produced not only lower unemployment under Democratic presidents but also more economic output and income growth. In fact, over the past 60 years, the real incomes of middle-income families have grown about twice as fast under Democratic presidents as they have under Republican presidents. The partisan difference is even greater for working poor families, whose real incomes have grown six times as fast under Democratic presidents as they have under Republican presidents.

Of course, past performance is no guarantee of what will happen when the next president takes office. However, given the striking fidelity of both presidential candidates to their parties' traditional economic priorities, the profound impact of partisan politics on the economic fortunes of American families over more than half a century ought to weigh heavily in the minds of voters.

• Larry M. Bartels directs the Center for the Study of Democratic Politics in Princeton University's Woodrow Wilson School of Public and International Affairs. He is the author of "Unequal Democracy: The Political Economy of the New Gilded Age."