LOS ANGELES (Reuters) - Batman narrowly fended off the new "Mummy" sequel to lead the weekend box office in North America for a third weekend, while moviegoers rejected Kevin Costner's new political comedy "Swing Vote."

"The Dark Knight" earned $43.8 million for the three days beginning Friday, distributor Warner Bros. Pictures said on Sunday. Universal's "The Mummy: T**** of the Dragon Emperor" followed with $42.5 million.

Walt Disney Co's "Swing Vote" came in at No. 6 with just $6.3 million, the latest disappointment for Costner, who has not had a $100 million movie since 1992's "The Bodyguard."

The total for "The Dark Knight" rose to $394.9 million. Warner Bros., a unit of Time Warner Inc, said it expects the film to add at least $100 million, likely becoming the No. 2 movie of all time in North America. "Titanic" holds the record with $601 million, ahead of 1977's "Star Wars" and its two reissues with $461 million.

"The Mummy: T**** of the Dragon Emperor" came in below pundits' forecasts of an opening in the $50 million range, bruised by the Batman juggernaut. The Brendan Fraser film actually beat "The Dark Knight" on Friday but the reigning champ bounced back on the next two days. (The Sunday component of the data is an estimate; final data will be issued on Monday.)

Universal, a unit of General Electric Co, said "The Mummy" was big internationally. The film, set in China and co-starring Jet Li and Michelle Yeoh, opened to $59.5 million from 28 territories.

Fraser has had a low profile since appearing as part of the ensemble in the Oscar-winning 2004 movie "Crash." But he now has two movies in the top 5, with "Journey to the Center of the Earth" at No. 5 with a four-week total of $73.1 million.