Word had it some years ago that Jeff Cohen, founder of the liberal media watchdog group Fairness & Accuracy In Reporting (who was also producer of the Donahue show on MSNBC right after he got booted from the network for being too critical of the build-up to the Iraq War), had often had spirited off-camera debates with Hannity during his years as a commentator. Jokes about a possible Hannity and Cohen show were squashed when Colmes got the spot. The logic is obvious enough. Though Colmes is a smart guy, Cohen's uncompromising style of attack would have likely overwhelmed the telegenic Hannity, and we all know that would be a serious no-no on Fox.
Though slightly garbling the sequence of events–Colmes already was Hannity's co-host at the time–janus certainly is right about Cohen's "uncompromising style"… and about Fox's strong aversion to progressive vs. conservative debates that it thinks the conservative might actually lose.
See FAIR's magazine Extra!: "An Aggressive Conservative vs. a 'Liberal to Be Determined': The False Balance of Hannity & Colmes" (11-12/03) by Steve Rendall