HUGH NICHOLS, whom many -- but apparently not enough -- Marylanders knew when he was a Democrat, is conducting an intriguing political experiment. He has turned himself into a Republican to see if being in a distinct minority will win him more supporters. And if you follow that, you may want to follow the race for governor in Maryland. Mr. Nichols, who is Howard County executive, tried unsuccessfully to stay in that race -- as a Democrat. In early May, he officially withdrew from the Democratic contest in a move that immediately fired up key scouts in the state's star-starved Republican Party. Although the Republicans won't choose their candidate for governor until next year's September primary, Mr. Nichols is suddenly No. 1 on their charts.

It's no longer the perfect name to invoke in Maryland, but Spiro Agnew comes to Republican minds as one who got to the State House when the winner of the Democratic primary turned out to be a loser in the general election. The latnario among GOP dopesters goes like this: If the Democrats choose Baltimore Mayor Don Schaefer, any Republican can probably forget it. If the Democrat is state Attorney General Stephen H. Sachs, large numbers of traditionally Democratic voters might prefer Mr. Nichols. And if it's anybody else -- House Speaker Benjamin L. Cardin, for example -- who knows?

There's one other hitch: All of these men are dancing around the ring, but no one has tossed his hat officially in. But the reappearance of Mr. Nichols in the quest for the governorship does give the Republicans an experienced and at least locally popular candidate. In a state where the GOP is outnumbered 3 to 1 in voter registration, turning to a Democratic turncoat for the top of the Republican ticket could be a shrewd move.