The disappointing debut for the "Dirty Harry" star's film, in which he plays an ageing baseball scout struggling with growing blindness, comes after the 82-year-old's eyebrow-raising turn at the Republican convention in August.
Eastwood "failed to hit a home run," said entertainment news website The Wrap, while Deadline Hollywood called it a "big disappointment" for the film icon, who talked to an empty chair and invisible Barack Obama in Tampa.
More broadly others in Tinsel Town will be disappointed at the overall box office takings, which were down nearly 30 percent on the same weekend last year, following a recent trend, Exhibitor Relations noted.
The 3D version of pioneering 2003 animated movie "Finding Nemo" -- 3D revivals are arguably another sign of the struggle to entice audiences out to the theater -- slipped from second to fourth place, with $9.6 million.
Sci-fi action-thriller "Resident Evil: Retribution," last week's number one, fell back to fifth place on earnings of $6.7 million.
"Dredd," a 3D production based on the comic strip Judge Dredd and its eponymous character, earned $6.3 million on its opening weekend, enough for sixth spot in the standings.
"The Master," a drama about a World War II naval veteran, starring Philip Seymour Hoffman and Joaquin Phoenix, jumped from a lowly 19th to seventh place this week on earnings of $4.4 million.
But "The Possession," a supernatural thriller starring Kyra Sedgwick, fell from third last week to eighth place, with $2.6 million in takings.
Rounding out the top 10 were "ParaNorman," an animated movie about a boy who can speak to the dead in ninth with $2.3 million, and Depression-era gangster tale "Lawless," with just under $2.3 million.
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