Three investment groups are competing in a high-stakes poker game here in which the winner will get to build southern Maryland's first -- and most likely only -- regional shopping mall and reap consumer dollars from the state's fastest-growing area.

Two of the developers have proposals for major shopping plazas within Charles County. The third wants to put a major multi-use complex on a 200-acre tract it owns in southern Prince George's County at the Charles County line.

All of the developers agree that they must entice at least three major national or regional department stores to their prospective sites to make the shopping mall gamble worth the risk. Whichever group pins down the anchor stores first is expected to break ground immediately. And while all three competitors are hoping to be under construction by summer so the new regional plaza can open its doors in time for the 1988 Christmas retail season, it is expected that only one will ever actually get built.

"Right now, it's a captive market down here. We're talking about 250,000 people in southern Prince George's, Calvert, Charles and St. Mary's counties with no place to shop," said Charles Stewart, vice president of Waldorf's Interstate General Corp., one of the groups trying to woo big-name department stores to the county.

Stewart claims his group has the jump on the other two projects because the 500-acre Westlake Village Shopping Center site is already zoned for commercial development, sits on the major regional highway and is within walking distance of Waldorf's planned community of St. Charles with its 25,000-plus residents.

But James P. Lee, vice president of development for Melvin Simon & Associates of Indianapolis is "confident" its Prince George's site in Brandywine "will be the only regional mall south of the Capital Beltway." Lee said the proximity to the beltway gives that site "better access to a larger trading area than the Charles site . . . . J.C. Penney's and Montgomery Ward's are joint-venture partners and so we already have an advantage over the St. Charles developers," Lee said.

Another developer, George Zamias, of Johnstown, Pa., will ask the local planning commission Monday to recommend commercial zoning for an 81-acre site near the intersection of Route 228 in Waldorf, but the final decision by county commissioners could be months away, according to planners. Zimias already owns 20 adjoining acres which would be more than enough space for a shopping center with a three large department stores, planners have said.

Neither Zamias nor his local zoning attorney were available for comment.

Stewart said, "Penney's and Ward's are not strong enough on their own to make a shopping mall concept fly." Lee agreed, but countered that Stewart's group has neither store and said he is confident Simon & Associates will get a third major store of the caliber of Woodward & Lothrop, Hecht, Sears, Bambergers or Garfinckel's in time to break ground this summer.

"Right now you've got three guys playing liar's poker. Everyone is wheeling and dealing as best they can. All three are trying to convince the other two developers they have a full house when no one does . . . . All three of us are talking to the same 10 or 15 stores," Stewart said.

Stewart says the department store executives he and Interstate's partner, Wilder-Manley & Associates of Boston, are talking with "are playing it close to their chests. They want to see who has the best deck."

If Interstate General gets the regional mall, the 500-acre site at Smallwood Drive and Route 301 will have two separate centers. A discount center between 250,000 and 300,000 square feet will be located on the southwest corner with the upscale town plaza, three department stores, movie house, medical and office space going in on the northwest corner.

Stewart said he expects to announce the major discount retailers later this month. A 40,000-square-foot medical complex is already under construction on the same tract, with banks, nurseries, toy retailers, restaurants and fast-food chains ringing the centerpiece mall, he said.

"We truly expect it to be a multi-use complex like Tyson's Corner. You have to remember Tyson's was once a farm and Crystal City was nothing 20 years ago. So we can realistically expect highrises in Charles in 25 years."

Unresolved water and sewer questions remain crucial to all three projects, as does simple road capacity in any development along the heavily traveled Route 301-Branch Avenue corridor. A major state transportion study on Route 301 is scheduled to begin this summer, but no construction money is committed.

Both Stewart and Lee say their investment partners are willing to make road improvements if the state does not act quickly enough. Stewart said his group will also give the state $1 million to get them started on a four-lane cross-county connector running west from Route 301 to Route 210 and the District, thus "giving us the best intersection in southern Maryland."

Charles County's Economic Development Director Ray Tilghman said the area has reached a critical population mass, has a very strong market and could easily support a regional center the size of Tyson's Corner.

Tilghman points to the new 200-room Holiday Inn -- which doubled its number of rooms after only four years -- as one indication that business ventures once considered risky in this rural county are paying bonuses.

"We are losing people to Fredricksburg, Springfield, Tyson's and White Flint malls who would obviously rather not spend Saturday in their cars," he said.

Stewart says with the 1980 census Charles moved up to third place in Maryland -- behind Montgomery and Howard -- in per-family income. The whole southern Maryland region has a per-capita disposable income of $8,305, he said. Per capita personal income for Charles County in 1982 was $10,409 for 1982 versus $12,383 for Prince George's, according to the U.S. Department of Commerce.

Much of this new buying power arrived over the last 20 years as some 100,000 new commuters and retired military people decided to call Calvert, St. Mary's or Charles counties home.

In the final analysis, Lee said, the decision will come down to site location and the track record of the venture partners. All say their business records are outstanding.

Lee said Melvin Simon & Associates is the nation's second-largest shopping center developer. The group built the Golden Ring Center in Baltimore, the Lynnhaven Mall in Virginia Beach and is currently developing the Pentagon City mixed use center in Arlington.

The southern Maryland shopping mall is the first Washington area venture for Interstate General's partner, Wilder-Manley & Associates of Boston. Stewart says the group develops and manages shopping centers in the Northeast, including the 1 million-square foot Yorktown complex in Chicago. Wilder-Manley are the remnants of the old Sidney Berenson Corp., "known as the father of regional centers," Stewart said.