Sean Penn, always up for a challenging role, is solidly planted in the I’d-watch-him-read-the-phone-book category. Given that, along with debut feature filmmaker Niels Mueller’s considerable abilities, The Assassination of Richard Nixon is compelling. But Penn’s willingness to test his audience, unfurling his unsavory side in playing an interpretation of Samuel Byck — who hijacked a plane in an attempt to mow down Tricky Dick, White House and all — is sometimes at cross-purposes with Mueller’s efforts to make Byck sympathetic. The writer-director, who went through the wars to bring his script to the screen, crafts a one-man-versus-the-phonies ethos that rings false, especially when set against the film’s otherwise unvarnished tone. That such a wretch as Byck would win the hand of Naomi Watts (who has little to do as the estranged wife) and the trust of Don Cheadle (who is graceful as the loyal friend and prospective business partner) is hard to believe. The lack of EXTRAS also serves to distance the enterprise from the wreck that was Byck.