ONE OF the surest ways to settle a grudge with a producer, legend has it, is to get him interested in a play about Abe Lincoln's doctor's dog. Any of these subjects -- Lincoln, doctors or dogs -- is guaranteed box-office poison. Put the three of them together and how can you possibly go right?

Herbert Mitgang, the author of "Mister Lincoln," which opens tomorrow night at Ford's Theatre, hopes to undo at least two-thirds of this venerable curse. He has written a one-character play that is not only about Lincoln but, in passing, about Lincoln's doctor -- his psychiatrist.

You didn't know Lincoln had a psychiatrist? Well, he wasn't actually a psychiatrist but a "general practitioner with a special interest in emotional problems," says Mitgang. His name was Anson Henry, and Lincoln went to see him in a fit of depression after Mary Todd's decision (later reversed) to break off their engagement.

"Dr. Henry diagnosed it as hypochondria -- acute self-pity," according to Mitgang. Another friend later recalled that Lincoln had suffered "two cat fits and a dog fit."

Of course, anyone who has seen "Abe Lincoln in Illinois" knows that Lincoln could be depressed. Didn't he carry a torch for Ann Rutledge all those years? Well, no, according to Mitgang. "There never was this romance between Ann Rutledge and Lincoln," he says. Recently unearthed correspondence has "totally disproved" it.

"I wanted to get across many of the things that I feel are misunderstood about Lincoln," says Mitgang. His views on slavery, for example: "He wasn't an apologist for slavery." In 1849 -- as Mitgang has written in a short, selective biography called "The Fiery Trial" -- Rep. Lincoln led a futile campaign to abolish slavery in the District of Columbia.

On the personal front, Mitgang disputes the general impression that Lincoln's family life was deeply unhappy. Historians, he says, have tended to make unjustified, retroactive assumptions from Mary Todd Lincoln's later troubles. As for them, three of her sons had died young (not to mention her husband's assassination), so she "had a right to go crazy."

Mitgang, a former editorial writer who now covers the publishing world for The New York Times, admits he has emphasized several aspects of Lincoln's career in order to score 20th-century points with 20th-century audiences: Lincoln was an intellectual, and a moral man. He proved we could have such a man in the White House. Might we again? He was an anti-militarist who knew how to stand up to the military. Mitgang has devoted a portion of his play to Lincoln's agitation against the Mexican War, a position that ensured that he would be a one-term representative. "He knew he was dead politically," says Mitgang. "He made some of the most anti-military and 'anti-American' comments that anyone has ever made." In a major speech in February 1848, Lincoln said President Polk knew that "the blood of this war, like the blood of Abel, is crying to Heaven against him . . . ."

"Mister Lincoln" is Mitgang's first play, and it will be the first Lincoln-related play to be performed at Ford's Theatre since its reopening in 1968. It will be, in a sense, Lincoln's first appearance there since April 14, 1865, when his unconscious body was carried across 10th Street to the "House Where Lincoln Died"

What attracted executive producer Frankie Kewitt to the play, she says, were not Mitgang's historical clarifications but the fact that, for once, Lincoln was recognizable as a fellow member of the species. "Everybody who's ever written a Lincoln play has sent it to me," says Hewitt, and in every play Lincoln "came across as a cardboard character. There was never any blood in him."

Hewitt had always hoped to do a Lincoln play at Ford's, but after years of reading and rejecting, "it just seemed to be impossible," she says. "I had given up."

In the case of "Mister Lincoln," she could do more than read a play -- she could see it. It was just quick flight away to Edmonton, Alberta -- where Mitgang's play had its premiere last October at the Citadel Theater, directed by Peter Coe and starring Roy Dotrice. Dotrice and Coe are British, and Hewitt believes that helped. They came to the material, she thinks, without having had Lincoln flattened the dehumanized through year after year of elementary-and-secondary-school American history instruction.

(Dotrice's nationality would have presented problems with Actors Equity, but for a rule that a Canadian production can be imported to the United States -- or vice versa -- if the entire company is left intact. Since Doctrice was and remains the entire company, he could thus slip through the barriers that usually exclude British actors from working here. But when he flew from London to Washington last week, he did so by convoluted way of Toronto -- in order to duck any unpleasant questions from immigration or Equity officials.)

Unlike Lincoln, Doctrice is not a tall man. But in a one-man production, there are ways around such difficulties. The scenery and furniture, according to Mitgang, have been built to slightly less than normal proportions, and the star wears elevator shoes. Although the play covers Lincoln's beardless pre-presidential years, Dotrice wears a beard throughout -- a natural one, grown for the part.

Such evidence as exists regarding Lincoln's voice and accent has yielded a slightly high-pitched, mid-western twang. In keeping with a contemporary newspaper account, this Lincoln begins a major speech with the words "Mister Cheerman . . ." And he is seen wandering through the White House corridors reciting Shakespeare soliloquies. "He loved the theater," says Mitgang.

If Mitgang's play helps us rescue Lincoln from eternal icon-hood, it could be just in the nick of time. Iran and Afghanistan have posed a bewildering challenge to our desire to be firm on the one hand, and understanding on the other. Here was an American leader who seemed to have an automatic sense of when to stand fast and when to yield, when to proclaim and when to listen. He sacked the generals who wouldn't chase the enemy hard enough, Mitgang points out, "and on the other hand he pardoned all those deserters. . . ." He was merciful, but "he could be tough as nails."