A Chequer-Board of Nights and Days

The screen fills with grainy footage of sprawling 1970s gas lines.

"Nothing's changed," Sen. Barack Obama says into the camera, "except now Exxon's making $40 billion a year, and we're paying $3.50 for gas. ... I don't take money from oil companies or Washington lobbyists, and I won't let them block change anymore."

Obama's ad, which has been airing in Pennsylvania as the April 22 primary approaches, is technically true but misleading, as non-partisan FactCheck.org and Hillary Rodham Clinton's campaign have been quick to point out.

It's accurate that Obama doesn't take money from oil companies; neither do his opponents, because corporate contributions are illegal. But Obama, like Clinton and John McCain, has accepted donations from oil and gas company employees -- $222,309 in Obama's case from donors from Exxon, Shell, Chevron and others, according to campaign-finance data. Two oil company CEOs have pledged to raise at least $50,000 each as part of Obama's fundraising team.