Every weekday, John Williams hosts a four-hour talk show from 9 a.m. to 1 p.m. on WGN-AM (720), walks 20 yards down the hall to a different studio at Tribune Tower, and, with just an eight-minute break in between, hosts another two-hour talk show from 1 to 3 p.m. on WCCO-AM in Minneapolis.‚ Both shows stream live online.

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While it may not be as physically demanding as the Dallas-to-Chicago-to-Dallas daily commute that Tom Joyner pulled off during his eight years as America’s “fly jock, it’s got to be every bit as challenging mentally and logistically.‚ Williams, 50, has been doing the six-hour, two-city, back-to-back shifts since April 13, and by all accounts, he’s managed to pull it off amazingly well.

How long will it last? The answer may depend less on Williams’ talent and stamina than on the precariousness of his situation at the Tribune Co.-owned news/talk station. That’s undoubtedly why he politely declines to discuss his status at WGN (where his contract runs through 2011 — although his bosses could opt out earlier) or his future at WCCO. “Both stations have a long history, are hugely successful and are pillars in their respective communities,” he said in a‚ statement. “I now get the best of both worlds.”

It’s not by accident that Williams finds himself on WCCO. He spent four years on the CBS Radio news/talk station in the Twin Cities before joining WGN in 1997. So when a vacancy occurred — and WGN general manager Tom Langmyer gave his blessing — Williams jumped. “John is a perfect complement to our afternoon programming,” WCCO program director Wendy Paulson said in announcing his return to the market. “He has stayed connected to the Twins Cities, he understands our community. He’s smart, articulate and is entrenched in the Midwest lifestyle.” Williams’ listeners also know that his younger son is about to graduate from high school and enroll at the University of Minnesota.‚ That’s one more reason to speculate that his future may be brighter at WCCO than at WGN, where he was yanked out of morning drive after only six months last June and replaced by Greg Jarrett, a newcomer from San Francisco. Underscoring his instability at WGN, Williams has bounced around three different shifts in the last year.

Through it all, Williams has been a consummate professional, upholding the standards of civility and respect for listeners that were the hallmarks of his WGN predecessors (including legendary morning star Wally Phillips, with whom he once worked as a college intern). Among his legion of fans is Eric Zorn, the Chicago Tribune columnist and uber-blogger who’s been a weekly guest on Williams’ show — along with fellow columnist Mary Schmich — for more than five years. (Their audio podcasts are available here.) Said Zorn:

“I often plug my digital recorder into the radio and listen to John’s show later in the day as I putter about, run errands and do chores.‚ I find that he hits a number of sweet spots as a talk show host. He’s opinionated yet not bombastic, critical yet not cruel, challenging yet not confrontational, smooth yet not slick, light yet not silly, serious and informed yet not wonky, self-confident yet not vain, experimental yet not self-indulgent, edgy yet not vulgar, topical yet not predictable and provocative yet not shocking.‚ It helps, for me, that he’s left of center politically. But I have many of the same positive things to say about WLS-AM 890’s Roe Conn, who’s right of center.”

WGN bosses once had sky-high hopes for the Joliet native and Southern Illinois University graduate. “The fit between John Williams and WGN is the perfect one,” former program director Mary June Rose told me when she hired him nearly 13 years ago. Think anyone in management would still say that today?