SALEM, N.H., JAN. 7 -- The question to Sen. Robert J. Dole (R-Kan.) went to the heart of the 1988 presidential race and any other political contest. What is the difference, Dole was asked at a Chamber of Commerce breakfast here, between you and your rivals, principally Vice President Bush?

"A lot depends on who we are," Dole replied. "Do they {the candidates} know about my problems or do they just want to be president?"

"I know a little about real people and real problems," he continued. "I know precisely where I'm from, precisely how I got where I am and I know how to get back where I'm from. I think I have been tested in my lifetime. I think I made it the hard way."

The answer neatly encapsulated the Dole campaign at this stage of the presidential race. In the absence of any discernible, major policy differences, Dole is mounting an intensely personal challenge to the frontrunning Bush, implicitly portraying him as a weak, out-of-touch patrician.

His message, in its bluntest terms, is that he is a stronger, tougher and better man than Bush and therefore deserves the Republican presidential nomination. His campaign theme is that he is "one of us." The wealthy and privileged Bush, by implication, is not.

Through three days of campaigning here this week, Dole returned repeatedly to this theme. He suggested that Bush has no record of leadership and described the vice presidency as "sort of standby equipment." As for Bush himself, Dole compared him to "that Maytag repairman" in television commercials "who sits year after year waiting for the phone to ring."

"When President Reagan wants help, I get the call from the White House," Dole said. "That's a big difference between myself and George Bush."

There is some evidence that Dole's jabs are having an effect. Bush complained earlier this week about Dole's disparagement of him and his record, warning the Senate minority leader to "get off my back." The brief exchange delighted aides to Dole, who begins the election year in the position to which all of Bush's GOP rivals aspire -- as the perceived main, and possibly only, alternative to a Bush nomination.

"We needed to shake things up," said Mari Maseng, Dole's press secretary. "George Bush is correctly running a status quo campaign. If everything stays the same, he wins the nomination."

By responding to Dole, "Bush gave us a lot more running room," Maseng said. But, she added, "you've got to watch where the line is and stay on this side of it."

The danger for Dole in crossing the "line" is that his portrayal of Bush as a weak leader with little understanding of ordinary Americans will be seen as heavy-handed, reviving the image of Dole from his 1976 vice-presidential campaign as a slashing political "hatchet man." But it is a risk Dole is willing to run in centering his campaign on the question of which of the Republican contenders has the proven mettle to take on the job of president.

"Which one of the candidates is strong enough and tough enough in the right sense to provide leadership?" he asked a group of supporters in Londonderry.

In taking this approach, Dole has submerged whatever policy differences there are between him and Bush, rarely mentioning specific proposals. More than the other GOP hopefuls, he emphasizes the dangers posed by the federal deficit and suggested here that a freeze on federal spending could be a "starting point" in reducing the deficit.

But Dole also told one audience he did not have precise figures on how much a freeze would save -- aides later said a three-year freeze on all discretionary spending would save more than $150 billion -- and he has not unveiled a full-fledged deficit reduction proposal. Nor has he yet developed a promised plan to provide long-term health care or tackled in detail foreign policy, for example in the Middle East, where Dole said the Reagan administration has been "sort of a spectator the last two or three years."

In an interview, Dole, who now shares Bush's millionaire status, made clear he intends to continue this approach, emphasizing why his personal experiences, including growing up in Depression-era rural Kansas and his struggle to overcome a wound suffered in World War II, set him apart from Bush.

"I understand the poor or the disabled or whatever," he said. "I've got a feeling for these people. If you don't have a feeling, you're not going to deal with {their problems} . . . "

"There is a rather wide gap in the way we look at things, the way we've had to look at things in our lifetimes. I don't say that critically of George Bush. I'm just saying there's a difference and he knows it and I know it. But do the American voters know it?"