With its enshrinement as The Greatest Film Ever Made safely assured and its box-office trajectory soaring ever upward, The Dark Knight is now being groomed for a spot so exclusive that it only changes hands once per decade: The highest-grossing film in history. Feel free to take the news with a grain of salt, seeing as it came from the notably math-challenged John Horn in today's LA Times; even so, it's hard to argue when Knight is looking at $400 million by this weekend and Titanic sits idle at the dock with $600 million. Seriously — $400 million in two weeks. But as we note after the jump, that last hurdle might be taller than it looks.Observers attribute the record haul-to-date in part to the same repeat viewers who bumped Titanic to No. 1; turnouts among "older moviegoers, families, Latino and African American audiences" are higher than normal as well. And last weekend, anyhow, The Dark Knight enjoyed the advantage of weak competition. Those days are over, though, with the execrable Mummy 3 nevertheless looking at a $50 million opening this Friday and Pineapple Express and Tropic Thunder set to usurp their own cuts of DK's marketshare in the weeks to come. By comparison, Titanic had 15 weeks at number one — most in the late-winter studio dumping grounds of early 1998, as Horn points out, and aided heavily by its inexorable march to Oscar glory. Similar factors could dovetail in unique ways for The Dark Knight, though, as its proximity to both the fertile July market and this fall's more prestigious film crop means Warner can revive its Terry Gilliam-endorsed Oscar chatter just in time to stretch DK's long tail into awards season. Call it Phase 2, even if Warners distribution boss Dan Fellman takes the high road with Horn: "We are honored to be considered in that company. But I think Titanic will hold that record for eternity." Don't sell yourself short, Dan! Or, more importantly, don't underestimate a James Cameron sabotage campaign — we're already seeing evidence of a conspiracy online. That's when you know you're a phenomenon.