IT is now time for American voters to give serious thought to the respective merits of George Bush and Robert Dole because the chances have been raised from possible to probable that one or the other will be the next president of the United States. The decisive change is due to the withdrawal of Sen. Sam Nunn of Georgia from consideration as the 1988 candidate of the Democratic party.
Political experts of both parties were in remarkable and unanimous agreement that Senator Nunn was the Democrat who would have been hardest for the Republicans to defeat in the 1988 presidential election.
The reason lies in the basic Republican strategy which has won four of the last five presidential elections beginning with Richard Nixon. Jimmy Carter, a southerner, was the one exception. That Republican strategy has been to win the white old South and meld it into a winning combination with the Southwest and far West.
The combination of those sections of the country won out twice for Mr. Nixon and twice for Ronald Reagan against candidates of the industrial and urban Northeast. The fact that George McGovern came from South Dakota is beside the point. He was the candidate of the northeastern big cities, as also was Walter Mondale. Mr. Carter, although a southerner, could only win once. He was no match the second time around for a Reagan whose strategy was aimed particularly at the whites of the old South.
Until or unless there is a profound change in the US political pattern (none is yet visible) the old South is likely to continue to be the key to the presidential election. Nunn could have held that key. He has the qualities and the postures which appeal to the old South. He is conservative, but moderately, not radically, in both domestic and foreign affairs. He also has won the respect of Congress and become nationally recognizable by handling defense issues sensibly and by making sense whenever he was on television during the Iran-contra hearings.
Conceivably there is a southern substitute for Nunn. Charles Robb is a former governor of Virginia, a son-in-law of Lyndon Johnson, and an ex-Marine with an excellent military record. Sen. Albert Gore Jr. of Tennessee comes from a distinguished southern political family. His father was a senator before him. Both are the objects of sudden interest among leading Democratic politicians. Could one or the other be groomed to take Nunn's place?
But they are the only ones among the present crop of visible Democrats who just might draw the old South back to its traditional allegiance to the Democratic party. And both are young. Both have yet to acquire a national image and national recognition.
All of which means that no matter how much harm Iran-contra may have done to the Reagan presidency the Democrats could still fail to capitalize on it by not naming an electable candidate.
And that in turn means that Vice-President Bush and Kansas Senator Dole are now well out ahead of all others of either party. Barring unforeseen and unforeseeable events the real election of 1988 may be fought out in the Republican convention between these two men.
One line of speculation in the aftermath of the Nunn withdrawal is that the Democrats will now try to persuade Gov. Mario Cuomo of New York to accept the nomination and then put Nunn on the ticket as the vice presidential candidate. That would relieve the senator from having to run in the primaries and let him keep his senate seat.
A Cuomo-Nunn ticket could make a good running. If there is an economic downturn before election day it could win. Since a sharp economic downturn now seems unlikely, there being too much momentum in the US economy, a good run ending in an honorable defeat would seem more likely.
Hence the serious queston is, which would be the better man, Bush or Dole, to wrestle the federal deficit and the unfavorable balance in US trade? Those two problems are at the top of the agenda for the next president.
Both are men of broad experience in Washington. Both know the machinery of the federal government. There are differences to learn about and to weigh in the days ahead.