The chances of hearing a liberal voice on local talk radio just got smaller. After Aug. 29, Pittsburgh will have to make do without the righteous indignation of broadcast veteran Lynn Cullen.

Because of major changes at WPTT-AM, Ms. Cullen and the low-signal station will part company after a decade. Although she has been the top-rated talk host there for years, she doesn't fit the financial advice and business feature format WPTT is betting its future on.

Fans of progressive politics and liberal talk are used to slim pickings in southwestern Pennsylvania, but things have never been this dire. With Ms. Cullen's departure from the airwaves -- and there is no reason to believe it will be permanent, given her popularity and ability to attract sponsors -- left-leaning thinkers will lose the most prominent, not to mention outspoken, ally they have in regional talk radio.

Yet voices like Ms. Cullen's are needed, especially during this historic election season, to bring balance to the political conversation. For more than two centuries, America's rich national debate has required a variety of perspectives.

That's why commercial radio has nothing to lose by making room for an occasional liberal voice. Not only would it be good for business -- it would be good for democracy, too.