Homer leaves work, and when he is reminded that his diet is starting on the first day of the month (which is that day), he decides to have one last binge at Springfield's Fast-Food Boulevard. After filling up, he decides to throw away his wrappers and the contents of his car in a trash can outside of a Krusty Burger, tossing away a leaky battery and a lit match. The acid from the leaky battery eats a hole in a gas main, with the lit match igniting the gas and starting a fire which soon causes nearby gas pipes to explode, completely destroying Fast-Food Boulevard.
At a town hall meeting, the enraged residents of Springfield demand that Fast-Food Boulevard be rebuilt immediately. To fund the reconstruction, a bond measure is proposed. As the next election isn't until June the next year, Mayor Quimby moves it to the upcoming Tuesday, making Springfield's presidential primary the first in the nation. Candidates and reporters head to Springfield when they hear the news.
The candidates flock to the Simpsons, who are undecided. Their home is filled with people and their yard is covered with reporters; helicopters and news vans surround the lot. When voting day arrives, an angry Homer and other citizens hold a meeting in Moe's Tavern. Homer suggests the people vote for the most ridiculous candidate, whom they choose after Chief Wiggum suggests himself. The same night, Kent Brockman announces an unexpected turn of events; Springfield has rejected all the leading candidates and voted for 8-year-old Ralph Wiggum. He wins the primary, much to the shock of Lisa Simpson.
Ralph is immediately embraced as the leading candidate, and Homer and Bart become his fans. Lisa, however, is miserable, as she knows how slow Ralph is. A news report (called Headbutt) shows Ralph has no idea of which party's nomination he is seeking. Both the Democratic and Republican parties contend to secure Ralph as their candidate. The leaders of both parties break into Ralph's home, wanting to fight for him. Lisa confronts Ralph amongst the media frenzy, attempting to convince him not to run. Ralph tells Lisa he wants to run so he can bring peace between warring parties and his earnest kind heartedness wins her support. He is proven to be a formidable candidate, and both the Republicans and the Democrats support Ralph for president. The episode ends with a political commercial for Ralph, sponsored by both parties.