Hello callinectes,
What, ya think liberals don't work for a living? Or pay taxes?
This is just a wild guess, but I wouldn't be at all surprised if liberals paid more taxes, per capita, than conservatives. Conservatives are disproportionately likely to fall into a few categories where effective tax rates are lower. One are business owners, who can use all sorts of tricks to lower their tax liability. If you have a guy whose business earns $150,000 and a person who earns the same $150,000 in the form of salary for a professional job, the latter is likely to pay more in taxes, since he'll be on the hook for payroll taxes and less able to play games to reduce taxable income (legally or otherwise).
Another category are retirees, who earn most of their money at the lower investment rates, rather than income tax rates like younger earners.