The southern and border state legislators who created the 1988 presidential "superprimary" celebrated their achievement today with the boast that they "will elect the next president of the United States."

The Southern Legislative Conference (SLC), composed of legislators from states between Maryland and Texas, heard conflicting predictions about whether the superprimary in a dozen or more states will help the Democrats or Republicans, a liberal or a conservative, a southerner or the New Hampshire primary winner.

But almost all of the legislative leaders agreed it will force candidates in both parties to spend more time in the South and give higher priority to the concerns of the region.

Former Virginia governor Charles S. Robb (D), who gave a brief, informal talk to the 1,700 legislators, aides and family members at a honky-tonk party tonight, was the speculative favorite of many in this predominantly Democratic group. Robb led all others for the 1988 nomination in a small, nonscientific poll of delegates taken by the Fort Worth Star-Telegram, with Vice President Bush favored on the Republican side.

But state Sen. John Traeger (D) of Texas, chairman of the SLC, said in an interview that Chrysler Chairman Lee Iacocca is "as well-positioned to move" in the South as anyone, and Speaker-elect Jon Mills (D) of Florida said Sen. Gary Hart (D-Colo.) or anyone else who wins in New Hampshire's 1988 leadoff primary could score strongly in the South.

Traeger and Mills were two of the major leaders in the push to line up southern and border states on a common delegate-picking day early in the presidential year. It has succeeded beyond their original expectations, with 10 states including Maryland setting primaries for Tuesday, March 8, 1988, and two more, Virginia and South Carolina, holding caucuses the following Saturday, March 12.

With legislative leaders in Texas and Arkansas pressing for a favorable vote next year and West Virginia -- the only state to reject the March date this year -- reportedly ready to reconsider its decision, Traeger said, "It is very possible 15 states" from Missouri to Maryland and south will elect one-third of the Democratic and Republican national convention delegates in the span of five days.

Gloating at the response of southern legislatures this year to the proposal the SLC initiated last year, Traeger said, "If we'd got this much action in the Civil War, we'd have won it."

Georgia House Speaker Tom Murphy (D), another of the kingpins in the regional effort, drew cheers when he said, "Us folks in the South are tired of being eaten over. We want to be recognized and we're going to be recognized . . . . The southern primary is going to elect the next president of the United States."

Michael Robinson, a George Washington University political scientist, told the legislators that the prospect of the superprimary is already affecting candidate schedules. "Fewer tickets are being purchased on Northwest," he said, "and more on Delta."

Bush and Sen. Joseph R. Biden Jr. of Delaware, a Democratic hopeful, canceled appearances at the conference today, but former secretary of state Alexander M. Haig Jr., a Republican prospect, and Rep. Richard A. Gephardt (D-Mo.) paid their respects, along with Robb.

Two political columnists -- Jack W. Germond of the Baltimore Evening Sun and former White House press secretary Jody Powell of the Los Angeles Times -- applauded the superprimary at today's panel, leaving former League of Women Voters president Dorothy S. Ridings the only naysayer. Speaking for herself and not her organization, Ridings said the regional contest "may be very factionalizing, it could mean more airport and TV campaigning, and it tilts us toward a disastrous national primary."

But state Sen. Chet Edwards (D) of Texas, prime sponsor of the unenacted March 8 primary bill in this state, said the regional primary could encourage some conservative Democrats such as Sen. Sam Nunn (Ga.) to enter the race, could offer incentives for more candidates to hang on even if defeated in New Hampshire or in the leadoff caucuses in Iowa, and could even "affect the thinking" of a liberal such as New York Gov. Mario M. Cuomo (D) by forcing him to address southern issues and concerns.

None of the legislators or panelists agreed with the Rev. Jesse L. Jackson's view that the regional primary will increase his influence. Instead, most endorsed Traeger's comment that "he Jackson will get his vote on March 8 or Dec. 25 and it won't vary 2 or 3 points."

Mills, Edwards and Maryland state Senate President Melvin Steinberg (D) all argued that because the key states in the new primary are larger and more diverse than Iowa and New Hampshire, they will provide what Steinberg called "a more objective forum to find the best candidate."