SACRAMENTO, Oct. 2 — Saying it ran “counter to the tradition of our great nation,” Gov. Arnold Schwarzenegger vetoed a bill on Saturday that would have automatically allocated all the state’s 55 electoral votes to whichever presidential candidate received the national popular vote.

The bill, which passed the state’s Legislature this summer, was devised by John R. Koza, a computer scientist who envisioned a system in which a series of states holding the number of electoral votes needed to elect a president — 270 — would commit their electors to casting ballots for the winner of the popular vote, regardless of how their individual electorates voted.

Mr. Koza said the goal was to force presidential candidates to campaign nationwide, rather than concentrating on a small number of battleground states — like Ohio or Florida — that have a lot of electors. California, while having more electors and voters than any other state, is considered reliably Democratic, and thus not often a part of the presidential campaign.

Thomas J. Umberg, the bill’s sponsor in the California Assembly, said that he was disappointed by the governor’s decision “to maintain the status quo” and that he would consider taking the proposition to a ballot measure.