I suspect the explanation will be that Miers’s firm, like lots of companies with PACs, spread their donations on both sides of the aisle (true), and that Miers wasn’t the one who decided how funds were distributed (probably true). WorldNetDaily — which the Boston Herald for some reason thinks is “left-leaning” — has the full story that the Herald re-reports in summary; the firm supported 14 Democrats and 10 Republicans in the 2000 cycle. And OpenSecrets.org reveals that the firm’s soft money donations favored Republicans in the 2000 cycle.
Her and her firm’s political donation history tell us very little about Miers. Not that I’m warming to the nominee; quite the opposite. Her reported support for racial preferences may be reason enough to hope her nomination fails.