Clarksdale, Miss. — Aaron Henry sits in the corner in his Clarksdale drugstore while a teen-ager serves customers at the old-fashioned soda fountain. Though the setting is from another era, the talk is high-powered in this pharmacy, which doubles as headquarters for black political activism throughout the state.
''We have to seek political power if we're to improve our conditions,'' says Mr. Henry. ''We're hanging on - to hold on to what we have.''
America's No. 1 problem is racism, Henry says.
''White folks still try to scare me,'' he says. ''This store has been bombed. So has my home. I know what it's like in Mississippi.''
But Mississippi has changed since Mr. Henry, who is a state legislator and president of the National Association for the Advancement of Colored People in his state, ran a losing but symbolic write-in campaign for governor in 1963. As he holds court in his store, Henry talks of the times when blacks ''had no rights in Mississippi,'' under such politicians as Sen. Theodore Bilbo and Gov. Ross Barnett.
Now blacks in Mississippi are voting in increasing numbers, and many hold public office. But there is currently a missionary zeal among black leaders and grass-roots workers to get even more black candidates running for office at the local, state, and federal levels.
During the Aug. 2 Democratic primary in Mississippi, activists worked hard to get black voters to the polls. And though some lawsuits have been filed over alleged voting irregularities, the statewide primary results indicated that Mississippi will wind up with at least 20 more elected black officials, most black leaders predict.
Around the state, organizers work in both urban and rural areas to elect black candidates. Cho-Cho Porter, a homemaker who lives in a housing project and who does occasional domestic work, explains how she registered more than 90 people in two hours near Oxford for the recent primary.
''I just talk to people and they show up to meetings, to register to vote, to do what's got to be done,'' she says. ''Things are better in Mississippi and I want to keep them that way. I'm not scared any more.
''I don't have a high school education, but I know what I want,'' she adds. ''The right to vote.''
Swaydie May Pettis, a homemaker who lives out in the country with her family and mother, says she supports register-and-vote activities because ''I remember that only 15 years ago, blacks had to risk their lives to vote.''
Two brothers, Charles and Leonard Brown, work in different ways. Charles, who owns a timber-products firm in Water Valley, says, ''I battle for black school superintendents and administrators because I believe in education.''
Leonard was shot and wounded July 27 by an unknown assailant while he was doing community service work. Many black people in the area suspect he was shot because of his involvement in getting blacks to the polls.
''I thought we had made progress, but I know the battle is still on,'' says Leonard Brown.
Aaron Henry lists what he sees as the 1984 election goals for Mississippi's blacks:
* Elect a black to Congress. ''Robert Clark is the man,'' says Henry. Mr. Clark, a state representative from Lexington, ran in the Delta area in a predominantly black district, but lost to a white Republican in the general election in 1982.
* Encourage blacks to run for every public office at the local level. Blacks should be willing to run as an independent or a Republican as well as a Democrat. ''White Democrats didn't vote for Clark in 1982,'' Henry says. ''We do not owe that party any undivided loyalty.''
A late entry into the Mississippi gubernatorial race was Charles Evers, brother of civil rights leader Medger Evers, who was assassinated in 1963. Charles Evers, who announced his candidacy last week, is running as an independent, on a platform agreed to by black leaders in Mississippi.
* Campaign vigorously among blacks. ''Don't take the black vote for granted, '' he said. ''Stop kowtowing to white folks to keep them from getting angry. Most of them don't vote for black candidates anyway.''
Henry and other black leaders have expressed dissatisfaction with the Democratic Party primary held Aug. 2, especially the voting in Greenville. There many of the voting machines broke down, and the election was delayed until Aug. 9.
To a visitor from the North, the new election day was just a routine day in Greenville, with temperatures pushing 100 degrees in the shade. Behind the scenes, worried black community leaders were scurrying for voters determined to stay away from the polls after being frustrated a week earlier. Final voter turnout was between 20 and 25 percent.
''I voted twice but I didn't like it,'' said Owen Brooks, who is active in civil rights in Greenville. Mr. Brooks worked in the North, but returned to Greenville 20 years ago to join the civil rights movement of the '60s and never left. ''Why did 70 percent of the voting machines not function at a time when black voters were lined up in the hot sun waiting to cast their ballots? I was mad enough to stay home, but I thought it was best to come back and vote.''
''I voted (at the second election) because the time is past due for us to get involved in local government,'' said Emmett Brock, who took some spare time after work to help bring people to the polls in his car. ''It was hard for most people to renew their enthusiasm and vote the second time around.''
No federal observers were assigned to Greenville on Aug. 2, although 322 were sent out to polling places in eight selected counties on that date. But US Assistant Attorney General William Bradford Reynolds detailed 70 observers to monitor the second vote.
The results of the Greenville election were good for blacks. The county's only elected black official, Willie Hamilton, was reelected coroner. Two women made the runoff scheduled for today for county circuit clerk and county tax collector, and two other blacks made the runoff for district officers.