NEW YORK — That huge sigh of relief coming from down the road emanates from the 30-plus theaters that won bookings for the first national touring company of “Wicked” — the road’s first monster hit since “Mamma Mia!,” or maybe even “The Lion King.”That softer sigh of regret heard in the background is coming from the same theaters — for underbooking. “Had we but known,” says Randy Weeks, president and chief operating officer of the Denver Center for the Performing Arts, where “Wicked” is playing a three-week engagement (Sept. 16-Oct. 2) at the 2,800-seat Buell Theater. “We went a little bit cautious with ‘Wicked,’ ” Weeks says about his calculated response to a few costly overbookings in recent seasons. But once the tour started out and response went through the roof, his reaction was: “Ooops! We should have had six weeks.” He has rebooked for 2007. That seems to be the pattern all over the road map, with one theater after another hastily scheduling future dates while cashing in on the phenomenal response to their initial offerings of the Winnie Holzman-Stephen Schwartz tuner. Return engagements already set for Toronto, Los Angeles and San Francisco will be considerably longer than their original runs of six and seven weeks. (Toronto is already locked in for 12 in 2007.) “We’re booking returns in places we haven’t yet gotten to,” says David Stone, lead producer on the show with Marc Platt. It was all part of a strategy to front-load the show, holding the initial bookings to modest runs, and then sign ‘em up pronto for return engagements. Stone recalls sitting in New York in early 2004 and wondering who in this vast land had even heard of “Wicked,” which opened at the Gershwin Theater in New York on Oct. 30, 2003. “We believed word of mouth about the show had hit the major markets by March,” Stone says, “but we were not sure that word had reached the rest of the country.” Striking out first for the big market towns of Toronto, L.A., San Francisco and Chicago was one way of hedging early bets. Another way was to tighten the booking reins. “We felt that there were some recent tours that went into some cities and overdid it,” Stone says. “We’d rather be selling out every single week and leave and come back again, rather than stay too long and leave empty seats.” That train of thought happened to coincide with received wisdom from the road. Local presenters who had picked up the book-long-and-book-often habit during what people still call “the Cameron Mackintosh era” of megahits had been burned too often by promising productions like “The Producers” and “Hairspray” that failed to connect in some road markets. “We had gone through an era in which we got used to the long bookings,” says Mike Isaacson, VP of programming at the Fox Theater in St. Louis. “But over time, we saw a detrimental effect on the subscription model. So the philosophy changed.” Other factors besides the soft performance of some shows contributed to the rethinking on presumably safe anchor productions. A sluggish economy, shrinking subscriber base and changes in theatergoing trends contributed to the current conservative philosophy on how shows are booked, advertised, marketed and sold. “There’s been a real lifestyle change in how people entertain themselves,” Weeks says of his Denver subscribers. “It’s much more spontaneous, and I don’t know if people are willing to commit anymore to something nine months away.” Watching the period for individual ticket sales get closer and closer to opening night, Weeks has even taken to saving some of his advertising dollar to use during the course of the run — “to get what I call the honey-what-do-you-want-to-do-tonight purchase.” But even as road presenters were making shrewd adjustments based on these shifting trends, a couple of witches were ready to pull something out of their hats. “Just when we think we understand what the philosophy of booking should be, ‘Wicked’ comes along and breaks all the rules,” says Isaacson, who short-booked a three-week run (Nov. 16-Dec. 4) at the Fox. “We like to say that’s six weeks in real-theater time,” he jokes about his 4,100-seat venue. The show is such a throwback, he says, it even confounds the latest advertising strategies. “We put in one print ad and the tickets just go! We haven’t had to run a single TV ad. There’s been nothing like that since the days of ‘Phantom’ and ‘Cats’ and ‘Les Miz.’ ” When asked how all this enthusiasm translates into box office, Nick Scandalios, VP of the Nederlander Organization (owner of the Gershwin and co-presenter on some road stops) sums it up: “You can’t beat sell-out.” But seriously, folks, “the fact that we’re only eight weeks into the Chicago run and we’re doing $1.2 million per week, I would say that the show has gone beyond our wildest expectations,” Scandalios says. Road presenters appreciate the coin, too. But more important, they say, is what “Wicked” can do for their theaters — and for theatergoing — in reversing negative trends. Big subscription houses simply can’t survive without a bona fide megahit to anchor their seasons, the kind of broad-bottomed show like “The Lion King” and “Mamma Mia!” that appeals to theatergoers across the board. When Broadway fails to produce such fare, the programming balance is upset, shows of marginal popularity are oversold and disgruntled subs drift away. Shows like “Movin’ Out,” “The Producers” and “Hairspray,” with their quirky appeal, are the bread-and-butter shows that keep subscribers happy (and theaters solvent) between megahits. Thanks to sophisticated demographic studies, major road houses know exactly how their audience breaks down and who, exactly, is going to go for “Monty Python’s Spamalot,” “Dirty Rotten Scoundrels,” “The 25th Annual Putnam County Spelling Bee” and even “Light in the Piazza .” What makes local presenters edgy is when a bare Broadway cupboard forces them to oversell. They need the real thing, and right now they are pinning their hopes on “Wicked.” Aside from delivering boffo advance sales, the show seems capable of bringing subscribers back. The true indicator of a genuine megahit, says Isaacson, is if it reels in subs. In St. Louis, “Wicked” bumped subscriptions at the Fox from 13,000 to 16,000. “That’s fantastic,” says Isaacson, who went through “a dark night of the soul,” wondering if auds even cared about live theater anymore. ” ‘Wicked’ is the affirmation that it’s really time for theater’s return.” Nowhere is that feeling of rejuvenation stronger than in Chicago. After playing for seven weeks at the 2,200-seat Oriental, the national company of “Wicked” flew to the next booking, leaving the physical production in place for a local company to move in for an open-ended sit-down run July 13. Those “Wicked” sales were so brisk — selling out its initial five-week run in a single day and necessitating a two-week extension — that “it was deemed the fastest-selling show in Chicago ever.” says Eileen La Cario, VP of Broadway in Chicago. The show continued to sell out when the local Chi company slipped into the vacant red shoes of the departing tour production, which grossed $1,203,886 and never did less than 100% capacity. Seven weeks into the sit-down and 14 weeks since the show first blew into town, “Wicked” hit an attendance mark of 250,000 people — with no signs of slowing. La Cario calls it “a Midwest show” because “it has the consummate good values and the warmth of the Midwest.” One reason the show is proving to be such a juggernaut, she opines, is that Oz and Chi are sister cities. Frank L. Baum, author of the original books, lived in Chicago and Oz Park is one of the city’s top draws. Chicago gets Oz.