Rep. David R. Obey (D-Wis.), one of the critics of the Gramm/Rudman/Hollings budget proposal, is right about one thing in his op-ed article of Oct. 25: We should begin to balance the federal budget before the 1986 elections.

"If we are going to get serious about reducing the budget deficit, then let's get serious about starting now, with the FY '86 budget, because there are sound economic reasons for doing so," urges Mr. Obey.

Lucky for him, the Gramm/Rudman/Hollings legislation will do exactly that.

In fact, the five-year budget process created by the proposal will take effect immediately upon passage into law this year, opposition political rhetoric notwithstanding.

To avert an across-the-board cut in the next three weeks, the president will have to veto more bills in a few days than he has rejected during the entire previous five years of his presidency.

I hope Mr. Obey is ready to sustain those vetoes. I am.

On Jan. 15, 1986 -- nine months before the 1986 elections -- the president will be required to submit the toughest budget of his presidency, with a deficit of no more than $144 billion.

That figure is $40 billion to $50 billion below the true deficit level as it now exists.

By May 15, 1986 -- six months before the 1986 election -- Congress will be required to pass its toughest budget ever.

And finally, on Oct. 1, 1986 -- one month prior to the 1986 election -- the president will have no legal recourse but to adminster an across-the- board cut in federal spending if Congress has failed to reduce the actual deficit to $144 billion.

Among the more cynical and disingenuous attacks on Gramm/Rudman/Hollings is this "why-not-do-it-now?" complaint arising among those whose political futures are rooted in avoiding a balanced budget at any cost. These are the same people who gutted the 1986 budget and who show no inclination to ever meeting its inadequate goals for deficit reduction.

Those who fear the political impact of Gramm/Rudman/Hollings do so because if they continue failing to do their jobs, they will have ample opportunity to explain themselves directly to their voters in the final, critical days of their reelection campaigns.

Actually, the ones who are in danger from those voters won't have to wait until 1986 to find they have been fingered because they already know who they are, and their votes on Gramm/Rudman/Hollings will demonstrate it.

They are the elected officials who have constructed careers by purchasing votes with the taxpayers' money and who are only now discovering that the American people are fed up with mortgaging the futures of their children and grandchildren to deficit finance incumbent longevity.

Indeed, when President Reagan asks for help in balancing the budget to assure prosperity and opportunity for our children and grandchildren, the Obey axiom answers, "Not me. Not now. Not ever."