When George Horatio Smith was laid off his job at a Cleveland auto assembly plant five years ago, he came to Washington and set out to make it on his own selling watermelons on the corner of North Capitol Street and Riggs Road NE. Today his business, called "Cowboy's Place," is booming, and it includes not just watermelons and pumpkins, but also wicker furniture and tropical plants.

Smith, 33, who wears a cowboy hat, scarf, boots and blue jean jacket, boasts that he supports President Reagan for reelection. What makes this Marlboro Man of the '80s unusual is that he is black -- a rarity within the Republican Party, which for years has been criticized for writing off minorities.

"Ronald Reagan came in and lifted regulations that were holding back a lot of small entrepreneurs like me," Smith said last week in explaining his support for the president. "I'm my own man, and now I can feel the power."

The few D.C. blacks who voted for Reagan four years ago were truly a silent minority -- defensive of criticism that they had sold out in favor of a candidate who seemed bent on dismantling virtually every program meant to help minorities.

Today their numbers have grown a little, contend local GOP party officials, who have made a top priority of recruiting minorities. And those die-hard black Republicans who stood by Reagan in 1980 have been joined by people who find virtue in the president's brand of economic conservatism and tough law-and-order talk.

"I think people are beginning to understand that all of the propaganda put out by the Democrats is not true," said Alice Banks, an accountant at the Sheraton Washington Hotel who served as a delegate last summer to the Republican National Convention.

"You'd be surprised at the number of black Democrats and independents who are changing their votes," she added. "I'm not talking about people looking for handouts. I'm talking about thinking people."

Clarence McKee, a black attorney who is chairman of the D.C. Reagan-Bush committee, predicted that Reagan would double his 1980 showing in the District, when he received 13.7 percent of the vote against President Carter. Reagan will do this, McKee said, with the help of a lot of "closet" black supporters.

"Either black Americans will vote their basic economic and political interest . . . or they will, as they have done in the past 50 years, cast their votes with a blind loyalty and allegiance to a Democratic Party," McKee said recently.

However, while the Republicans' rhetoric about making inroads with black voters has become bolder in recent days, there is little hard evidence to back it up.

A mid-October survey by The Washington Post and ABC News found that 16 percent of the black voters interviewed intended to vote for Reagan instead of Democrat Walter F. Mondale -- roughly the same percentage of blacks who voted for Reagan four years ago, according to a New York Times-CBS News exit poll.

The Washington Post-ABC survey revealed that many blacks, while philosophically or morally sympathetic to Mondale, nonetheless felt they were better off financially with Reagan in office. Some also expressed disenchantment because Jesse L. Jackson was unable to obtain major political concessions from Mondale and other Democratic leaders.

A new Washington Post-ABC News poll released this weekend shows that one in 10 black voters plans to vote for Reagan on Tuesday -- a statistically minor decrease from the earlier showing.

Al Russell, owner of Glass House Opticians, 1227 Good Hope Rd. SE, and president of a group of Anacostia business persons and professionals, said he has not seen much support for Reagan in his overwhelmingly black part of town.

"The bad point is that a lot of guys went out of business after Reagan came in," Russell said. "For the first two years of his administration, small businessmen just crashed. The guys still around here are holding on by a string."

"It's a wait-and-see matter," he said. "We hear a lot of money will come down" through "enterprise zones" and grants during a second Reagan administration, "but we're waiting to see."

Still, Republicans insist that black support for Reagan is growing and that closet supporters -- the ones who are reluctant to tell pollsters or anyone else of their true leanings -- will turn out on election day for the president.

"We think D.C. is an appropriate place to start this effort to bring more minorities into the Republican Party," said Ann Heuer, chairman of the D.C. Republican Party, during a campaign reception Friday evening that was sponsored by a coalition of blacks, Hispanics and Asians.

"We're pleased with the turnout because . . . it shows that this is a party of opportunity and that we are not just a bunch of elitist country-clubbers," said Heuer, who is white.

Reagan has made remarkable inroads among young people, registering more than a quarter of a million students across the country this fall, and some of that support has come from blacks.

"Just as the president increased the economy for the entire nation, he's improved economic conditions for blacks," said Deroy Murdock, 20, a black student at Georgetown University and college coordinator for the D.C. Reagan-Bush campaign. "But I wouldn't limit it just to the economy. Black people see a strong leader in Reagan ."

Sylvester E. Williams, a 23-year-old economics and business student at Howard University who founded the College Republicans Club at Howard in 1982, said he favors minimum government interference in the marketplace and a strong national defense. His club has grown from 12 to 25 members in the past two years.

While most black students are influenced in their political thinking by their parents, Williams said, when they get out on their own they discover a lot that is appealing about Republicanism. "Black kids, when you ask them questions, are all fiscal conservatives," he said.

Black Republicans in this 80 percent Democratic city include diverse groups, from the old moneyed blacks whose fathers and grandfathers were Republicans to career federal government employes and government appointees who owed their jobs to Republican administrations.

Others were drawn to the Republican Party by Jerry Moore Jr., who became active in local Republican politics nearly two decades ago and subsequently was appointed and then elected to the City Council. Moore this year is struggling to hold on to his at-large seat with a write-in campaign, after losing to Carol Schwartz, a white former school board member, in the Republican primary.

But with few exceptions, black Republicans have operated outside of the local Republican Party system, which for many years was dominated by whites who had little interest in allowing black members inside.

Herbert Reid Sr., the legal counsel to Mayor Marion Barry and a longtime civil rights leader, recalls that for years conservative blacks wanted to be part of the party but were constantly frustrated. "There's such a yearning, but they kept getting the door slammed in their face," Reid said.

There are many reasons why blacks have stuck with or turned to the GOP. Some say they believe that less government is better for blacks in the long run because it forces blacks to do more for themselves. Others believe that blacks have been taken for granted by the Democrats for too long.

Charles E. Tolson, owner of a moving and storage company and chairman of D.C. Black Voters for Reagan-Bush, said that in the past, some of his workers would stay on the job a while and them drop off to collect unemployment. That has changed under Reagan, he said.

"Now, people want to work," he said. "They're coming back to work and they're staying."

Thomas Watson, 38, a native of Cleveland and owner of Watson, Rice & Co., the largest certified public accounting firm controlled by blacks, switched from Democrat to Republican in the mid-1970s.

"I feel we as blacks have spent too much of our energy and effort in the wrong direction," he said. "We ended up with short-term benefits instead of long-term jobs. . . . What has happened over the last four years has been good for blacks in general. . . . We have a more free and open economy."

Orlando Darden, a business broker and chairman of the D.C. retirement board, became a Republican to support Jerry Moore. "I like the idea of work and sacrifice," he said. "I like that, and I have no regret about that as I pass the work ethic on to my two sons."

Cardell Shelton, 54, a lifelong D.C. resident who runs the Southeast Construction and Maintenance Co., thinks that Democrats are indifferent to the problems of Anacostia -- "only pennies come to Anacostia" -- and that he is better off fighting for change as part of a minority party.

"The economy is up, jobs are plentiful, food is bountiful on the table, and the only ones catching hell are the 'bougie' black middle-class, the social workers, the poverty pimps," he said. "I like Reagan saying, 'Come on, you have a chance to go to work. If you don't want to work, then to hell with you.' "