Lou Cannon, able White House correspondent for The Post, reported Wednesday that President Reagan had planned to deliver a speech citing a Jimmy Stewart movie to reinforce his position that only a corrupt Senate would reject Robert Bork for the Supreme Court. The White House staff nixed it, wrote Mr. Cannon, because they felt it was too inflammatory and controversial.

Who would have thought that this all-American classic -- "Mr. Smith Goes to Washington" -- which in rather simplistic fashion shows that virtue can triumph over evil, even in the Senate, would get on a White House hit list?

This film is the work of Director Frank Capra, famed for his magic touch in converting corny plots into great movies, such as that Christmas perennial, "It's a Wonderful Life," also starring President Reagan's close friend Jimmy Stewart. The president's instincts were good; the reference to "Mr. Smith Goes to Washington" would play well in Peoria, but it was hardly the time to tell the Senate it knows not what it does.

Well, the White House staff can muzzle the president, but they can't shut me up, so I'll tell you about "Mr. Smith Goes to Washington." Controversial and inflammatory, indeed. Here's a clean-living lad who's sent to Washington as the junior senator by the corrupt party boss. The sly plan is to keep the aging senior senator in charge, minding the store as well as the party strong man; the youngster will simply take orders.

They sure had Jimmy Stewart all wrong. He takes on the senior senator, the political bosses and then the whole Senate. There are these greedy real estate developers who are moving to wipe out the proposed national boys' camp on the lake and turn it into a profit-making enterprise. Jimmy Stewart delivers a resounding speech on the floor against the powerful interests, spells out the American Dream and turns the "lost cause" into thundering victory, with the whole country aroused and cheering. The corrupt senator's career is finished, and with abject humility, before the fade-out, he says he's not fit to hold public office. Up on Capitol Hill, at the time, they thought it was a Capra comedy.

There is a sequel to this. Some years back, Howard K. Smith, foreign correspondent and news commentator, ran into trouble with his weekly half-hour show on ABC originating from Washington. He aired a program that angered Richard Nixon and his backers, many of them big TV sponsors. The ABC News boss, Jim Hagerty, who had been President Eisenhower's press secretary, publicly supported Howard Smith, but the network moguls knuckled under and put the distinguished commentator out to pasture. He could continue his weekly show on ABC, but it was to stay away from controversial subjects. The producer decided to take the program temporarily out to Hollywood, which was about as safe a place as any in those days.

At the time, I was a struggling free-lance writer in movieland. Howard Smith asked if I'd help line up guests for his interviews. This was going to be a piece of cake. Was I wrong! Warner Brothers told me it "wouldn't let that commie on the Warner lot." A couple of directors and actors with left-wing leanings declined to cooperate because they felt Howard Smith was too right-wing for them. Things weren't going too well.

Joe Mankiewicz, one of Hollywood's outstanding writers and directors, had just returned to California after two years in Italy filming "Cleopatra" with Elizabeth Taylor and Richard Burton. He agreed to an interview on one condition: that there first be a leisurely lunch, just Howard Smith and him, and that the talk be only about politics and world affairs -- not a mention of the movies.

Word of this got around. Mr. Mankiewicz was probably the only intellectual in the movie industry with a respectful following among the riffraff because his pictures made money. Suddenly there was a stampede of stars and directors wanting to be on the show, resulting in so much good footage that the producer later carved it into two half-hour shows. All he needed was a catchy title. They tried some of the old chestnuts: "The Real Hollywood," "Secrets of Movieland," "The Changing Face of Hollywood" and so forth.

I made an offbeat suggestion. The producer and Howard Smith loved it: "Mr. Smith Goes to Hollywood." But ABC turned it down. Too controversial.