On the flat Kansas plains, Bob Dole today began a long uphill climb to be president of the United States.

"I have no illusions about the magnitude of the undertaking," the Republican U.S. senator told a hometown crowd whose size was unofficially estimated as almost everyone in this population-5,600 town. "Financing, logistics, simple human effort or the lack of these may conspire in time to defeat a candidacy, but they cannot deter it at the outset."

At the outset, Bob Dole, two-term senator and President Ford's running mate in 1976, is the presidential choice of 1 percent of the Republicans surveyed in public opinion polls. And while he said at a press conference today that he is "not totally certain" he can win the GOP nomination, he added, "we all have our scenarios or we wouldn't take this step."

For Dole, 55, that scenario is: build a coalition of veterans, the handicapped, farmers and ethnic groups that in small states like Iowa and New Hampshire (where his aides say his personal campaigning is most effective) can have disproportionate influence. Win there and let momentum carry him through the middle and later primaries next year.

Dole's announcement, a 21-minute philosophical view of America today, came as no surprise. What was unusual was that a subdued Dole delivered it-not the wise-cracking man in the U.S. Senate, not the gutfighting gunslinging presidential running mate, but instead the presidential hopeful who wants himself and his 1 percent taken seriously.

And seriously it was taken in Russell, as the town gathered under the Amercian flag in front of the one-story yellow-brick city hall at 8th and Maple. It was America's rural past offering the nation leadership for the future.

But Russell, despite its now-prospering cattle industry and the flush of affluence from the bobbing oil pumps in the wheat fields, is troubled nonetheless.

Kittycorner from city hall, American Agriculture Movement members, wracked by low wheat prices, parked farm equipment on a vacant lot, seeking to make the tractor factor a force in politics.

A sign inquired, "Mister Dole! Where Were You When We Needed Your Support in Washington?"

And there was agreeable applause when Dole portrayed America as a country that has gone astray and must return to its historic values:

"This is my concern in the campaign ahead-to let America be America again . . . It is arrant nonsense to suppose that because [people] may not be equal in ability and ambition, government should equalize their portion of the material advantages which flow from the unfettered exercise of ability and ambition.

"If we can eliminate this and similar misconceptions about the purpose of government, then we can get away from building the federal budget and the federal bureaucracy and get back to building the nation."

More applause.

Although he said he would not "attack the incumbent president," Dole characterized President Carter's foreign policy as a "grave, dangerous confusion."

Dole pledged, too, not to attack other Republicans in the race for his party's nomination. That would be a startling change for a man who has never been reluctant to engage in pitched battle. "It's going to be a hard campaign [but] we are not going to try to mow down the opponents," he told a press conference at the Russell Volunteer Fire Department, where his father served for 51 years.

A short time later he was off, through city hall, greeting workers and passers-by by their first names. This is, after all, the town where Bob Dole came to heal, as he reminisced today, after his right arm was wasted by war more than 30 years ago.

It was a scene somewhat like that of 1976 when the newly nominated Republican vice-presidential candidate returned to Russell with Jerry Ford to begin their campaign.

As this morning wore on, Dole departed Russell for Iowa and eventually New Hamshire, where in precinct caucuses and a primary election the nation's first contests of presidential popularity will be played next year.

"That's the hump. He has to get over that hump," said campaign manager Tom Bell. "If he's blanked out in the early states, he's blanked out."

These are rural states where personalized politics are most effective, Bell said. "If we had to rely on media, we'd be sunk."

Bell predicted a "quick winnowing" of GOP candidates. "The Republican party," he said Sunday night during a reception for Dole in the Rojo Room of the Russell Ramada, "can't sustain five or six candidates."

If Dole's presidential bid falters, he might still be able to run for reelection to the Senate. His current term, which he won with 50.9 percent of the vote in 1974 after lagging most of the campaign, expires next year, but the filing deadline is June 20, 1980, late enough for him to evaluate his presidential chances.

Former president Ford has sent a fund raising letter to garner money for any Senate reelection bid.

Today, Dole also fielded questions as to whether he could win Kansas' first presidential primary April 1.

The two most talked about potential opponents of any Senate reelection bid say they would make Dole's presidential angling an issue against him in a Senate campaign.

"I'm willing to take my chances," Dole said of his presidential efforts. But of the Ford fund-raising, he said: "I'm going to cover my bets." CAPTION: Picture 1, Wide-angle lens captures the scene at 8th and Maple in Russell, Kan., as two-term Sen. Bob Dole sets out from home in quest of the Republican presidential nomination. AP Photos; Picture 2, With mother Bina and wife Elizabeth, the candidate accepts plaudits of townspeople.