In every election since Ronald Reagan dramatically reduced marginal income-tax rates, Republicans have debated whether taxes are a potent issue. As more and more taxpayers come off the rolls altogether (over 30% of tax filers now pay no tax at all), some argue this has lost its punch. But there is nothing like a financial meltdown to focus attention on this issue.

As this report explains, John McCain is highlighting Barack Obama’s plan to hike taxes. What started as a general tax hike has become a tax on the “rich,” but in a limping economy even that is problematic:

Republicans are hoping that the old antitax strain remains strong this year. Sen. McCain is pushing for a permanent extension of the tax cuts enacted by Mr. Bush, which are set to expire at the end of 2010. Among other things, the plan would keep the top income-tax rate, paid by the wealthiest Americans, at 35%. Absent an extension, the top rate would rise to 39.6%. Sen. McCain is also pushing a new tax benefit for middle-class families, promising to double the exemption that can be claimed for dependents.

“The reality is raising taxes in a weak economy is a bad idea, and we don’t,” said McCain campaign policy chief Doug Holtz-Eakin, adding that higher individual rates would hit small businesses particularly hard.

Polls suggest Sen. McCain has room to exploit the issue. Even though Sen. Obama has vowed the middle class will get tax cuts, not tax increases, 49% of voters said they believed their taxes would go up if the Democrat wins, according to the latest New York Times/CBS News survey.

Moreover, voters are simply becoming more savvy (or cynical, depending on your perspective) and simply don’t think the “rich” will be the only ones hit:

At the McCain rally Thursday in Iowa, Kate Julicher, 25 years old, said she is not persuaded by Sen. Obama’s promise to cut taxes for people like her. She doesn’t believe he will raise taxes only on couples earning more than $250,000 a year. “I don’t believe him,” said Ms. Julicher, a software engineer from Cedar Rapids. “I have a feeling that $250,000 limit is going to come down when they realize they need more money to bail out whoever they bail out.”

There is an opening there. How large and how effectively McCain can exploit it remains to be seen. But tax-hikers haven’t done well in the past–Walter Mondale, anyone?–and it’s hard to see how that approach wins votes when Americans see major financial institutions teetering on the brink of collapse.