Bud (Costner) is a Budweiser-swigging, egg-packing divorcee from a town you've never heard of.
Yet he finds himself holding the balance of power when it miraculously transpires that his vote is the one the whole country depends on to elect the next government.
His 12-year-old daughter, teed off with his socially irresponsible ways, had sneaked into a polling station in the backwater of Texico, New Mexico, to vote on his behalf...but the system crashed.
However, it's not just any old spoilt vote - by some bizarre quirk of fate it's the one that will decide who takes over at The White House.
Reacting quicker than Dubya to the September 11 attacks (not difficult), both the Republicans and Democrats twig that they need Bud onside if they are to seek office.
Republican incumbent President Andrew Boone (Grammar), aided by campaign manager Stanley Tucci, immediately redirects Airforce One to its new home in the desert.
In the red corner, Democratic hopeful Donald Greenleaf (Dennis Hopper), guided by spin doctor Nathan Lane, heads south to secure the hapless Bud's all-important cross-in-thebox.
Over-reacting to every utterance by the bewildered uber-voter, they soon find themselves pin-balling across the political spectrum, cheerfully dumping established policies in the rabid pursuit of power.
So Boone becomes a environmental standard-bearer while Greenleaf finds himself fronting an anti-abortion info-mercial where a playgound-full of nippers disappears in a puff of black smoke.
For a fair old while, this is good, boisterous fun. Costner is just dandy as the Willie Nelson-loving waster and newcomer Madeline Carroll is that rare thing - an American kid whose ear doesn't need clipping.
The cynical vote-chasing ploys of the political machines are cheekily spoofed....and then the grand conceit is deserted and the whole caboodle slides into a tacky vat of sentimental, flag-waving gloop.
It's a shame...because director Joshua Michael Stern hits some satirical bullseyes early on only to go all moist-eyed and weak-kneed.