Dwayne "The Rock" Johnson will get clobbered as a third-party Presidential candidate unless he's willing to stand up to billionaires and fight for everyday people ... so says the Green Party.
As you may have heard ... the WWE superstar-turned Hollywood megastar now says he'd seriously consider running for Prez "if that's what the people wanted" -- but Green Party spokesperson Michael O'Neil's not sure The Rock's got the stones.
O'Neil tells TMZ ... he doubts Dwayne is tough enough to deal with the dirty tricks both the Republican and Democratic parties would throw at him to "keep their guillotine chokehold on democracy.