"The first thing I do is think old."

Jim Morris, who's all of 25, was explaining how he prepares his impression of Ronald Reagan. He unveiled it the other day at a brunch cum press conference at Garvin's Comedy Club. Now and then you could've sworn it was the president himself.

"I was doing Reagan before Rich Little was doing Reagan," he said. "I started before the Republican convention. First I studied Reagan for several months. I watched him on television, did the groundwork of research -- his old films, transcripts of hearings of the House Un-American Activities Committee, movie outtakes, and lately I've been reading Lou Cannon's book. I had to think Reagan and feel Reagan before I even attempted the impression. Now I have banks of information in my subconscious."

The other day, as patrons toyed with eggs benedict and champagne, Morris made an opening statement from a lectern adorned with a presidential seal sporting a turkey instead of an eagle. Taller and slimmer than the genuine article, he made do with rouge, pencil lines, deftly applied lowlight and highlight and a few physical mannerisms -- which sufficed.

"A balanced budget," he said with conviction, "is much like a balanced diet . . . As a matter of fact, as Rudyard Kipling once said . . . Do you folks know what I learned just recently? . . . I'm a nice guy. I've got a lot of charm. . ."

He has caught much of Reagan's rhythm and style: the twinkling eye, the earnest gaze, the winning aw-shucks smile. Tilting his head, he blinks and grins; his walk is slow and feeble. More funny than fair, Morris at least sounds like the gent, his voice produced professionally from deep in the chest.

When a question comes from one of the tables -- "Is it true that you don't actually know the names of any countries in South America?" -- Morris says "Shut up!" Anger burns in the words, and there's a sense of theater, too -- like the president having his way with whiny hecklers.

The material -- from political lampooning to silly clowning, from gentle irony to out-and-out tastelessness -- is often enough for a chuckle and, less often, a belly laugh. Morris sings songs and recites doggerel as Reagan might ("Roses are red / Commies are, too / I visit Bonzo each day at the zoo"), and mixes and mangles advertising slogans to help things along ("Nine out of 10 renters recommend Trident for their navies who choose subs"). It's inventive at times but not, at present, enough for an hour on stage.

No fan of the president's politics, Morris might do well to give the devil his due. Ronald Reagan is more often terse than longwinded; he's polished and quick-witted more often than not. In the question period the other day, Morris scored only occasionally. Still, he seems to have made a promising start. LIVE IN CONFERENCE -- Jim Morris at Garvin's for brunch, Sundays at 1. 234-7143.