INDIANAPOLIS, Ind., May 6--"Ain't God good to Indiana? Other spots may look as fair, but they lack the soothin' somethin' in a Hoosier sky and air where the ripples on the river kinda chuckle as they flow--ain't God good to Indiana? Ain't he, fellers? Ain't he that."

So read a bronze plaque in a corner of the early Victorian Hoosier state house in Indianapolis. And if there is an issue in this primary campaign after Johnson's March 31st decision to withdraw and deescalate, it is Hoosierism.

Dispute rages among both press and campaign staff members about the origin of the name, "Hoosier," but reliable sources in the metropolitan Indianapolis area say that the word originated on snowy nights in pioneer Indiana. Tired travelers wandering their way West would knock on the doors of isolated log cabins, and from the inside a friendly pioneer would ask in his nascent midwestern twang, "Who's there?"

Proud Name

That simple question soon became the proud name by which Indiana residents now call themselves and everything good that goes on in their state.

Gov. Roger D. Branigin took his native Hoosierism and made it his platform. On scores of billboards across the state, in blue with white letters, the Governor's advertisements proclaim, "Vote Indiana, Vote Branigin."

On the radio every hour the Governor's spots rail against "Outsiders coming in to buy your vote" and then ask the honest Hoosiers to vote to uphold the honor of Indiana and vote for the colorless, rather elderly governor.

In the newspapers, large ads tell "why my husband is a candidate for president of the United States" by Mrs. Branigin--in which she explains how Hoosiers will demean themselves if they vote for an outsider.

Senator Eugene J. McCarthy has tried to meet the issue of Hoosierism in his quiet, reasoning manner. On many of his television advertisements, McCarthy says, ''''All I ask of you is to look at me in the traditional way in which the people of Indiana supposedly look at any candidate: with some restraint, and with reserved judgment."

The appeal appears to be working in McCarthy's favor during these last few days of the primary campaign as it did during the last weekend in the New Hampshire campaign. Many feel that the Minnesota Senator may be able to catch up with his quiet appeal.

Kennedy, unlike McCarthy, has chosen to ignore Hoosierism and appeal to indiana voters' national consciousness. He has attempted during his Indiana campaign to state national issues in Hoosier terms.