In Frankfurt, the Kentucky senate has voted to move its presidential primary to the second week in March. In Oklahoma City and Jefferson City, Mo., similar bills passed the House. In South Carolina the talk is that both state party chairmen will switch to an early March primary, as they can do under existing law. In Austin and Raleigh, both the speaker and the lieutenant governor will push for early March primaries in special sessions this summer. Three states -- Florida, Alabama, and Georgia -- already have primaries on what was called Super Tuesday in 1984. Now Florida's Gov. Bob Graham is predicting that two- thirds or more of the South will vote in primaries or in caucuses in that second week in March.

The move to a southern regional primary is spreading like wildfire. This threatens to change the way presidential candidates are selected, and some caution is in order. The impetus for the southern regional primary comes from Democrats who think Iowa and New Hampshire have had too much influence, and that the importance of organized support in small states has given unions, NOW, the NEA and gay rights groups too much visibility and leverage. A southern regional primary, it is said, would be more likely to produce nominees who could win general elections.

Good reasoning, as far as it goes. But the southerners should remember that Iowa and New Hampshire (plus Michigan for the Republicans) will still hold earlier contests, and candidates who do well there could sweep the southern contests a week or so later. Gary Hart, unknown to 99 percent of southerners Feb. 15, 1984, nearly did that 26 days later, and came close to locking up the Democratic presidential nomination. Given a crowded field, a southern regional primary could also result in a first-place finish for Jesse Jackson, who won plenty of southern primary votes in 1984.

The better procedure, we think, would be to spread the southern contests over three weeks. That would produce a regional contest, but would give voters a chance to winnow out candidates, watch how they act under pressure, and learn more about them than they can from one flight of 30-second ads. We don't give much weight to the argument that a southern regional primary would penalize unknown candidates: is it desirable for Americans to have a president they know little about? But we do think there should be some length and sequence to a campaign to place the candidates under a spotlight and subject them to rigors that approximate those of governing.

A single day of primaries that can decide the nomination all at once, after only two or three other states have voted, poses serious risks for a party and the public. The understandable desire of many Democrats to nominate a candidate who can win a general election should not blind legislators to the possible defects of the single regional primary.