WHEN REAGAN criticized Carter for opening his campaign in Tuscumbia, because of its Klan association, he damaged whatever changes he might have had this state. Local Republicans, longtime Reagan fans, are working hard for him, with help from Gov. Fob James' (D) wife, Bobbie, and her Moral Majority friends. But Carter's support ranges from black leaders to George Wallace. A Birmingham Post Herald poll in mid-September had it Carter 47, Reagan, 34, Anderson 5.

Public Service Commissioner Jim Folsom Jr. (D), son of the former governor, upset freshman Sen. Donald Stewart (D) in the runoff and gained a quick 15-point poll lead over retired admiral Jeremiah Denton of Mobile, the ranking POW of the Vietnam war and a Moral Majority favorite. Neither campaign is lavishly financed, but Folsom's name is far better known.

Rep. John Buchanan (R), a moderate, was upset in the GOP primary by insuranceman Albert R. Smith Jr., with the backing of the Moral Majority. Buchanan so far has been unable to get on the ballot as an independent, so the race is between Smith and another conservative, Birmingham City Councilman W. B. (Pete) Clifford (D). ARKANSAS (6)

IT LOOKS like an incumbent's year in Arkansas, from the top of the ticket to the bottom. After some shaky early polls, Carter has moved into a faorite's position. A well regarded poll, taken Sept. 16-20 by KATV-Doubleday Co. of Little Rock, had it Carter 48, Reagan 39 and Anderson 6.

Gov. Bill Clinton (D) and Sen. Dale Bumpers (D), two men with national ambitions, are heavy favorites for their second terms. Clinton has a capable opponent in Frank White, a savings and loan president and industrial development leader, but is far ahead.

Bumpers has a 76-19 percent poll lead in his race with Little Rock investment banker Bill Clark. Freshman Reps. Ed Bethune (R) and Beryl F. Anthony Jr. (D) have entrenched themselves in their House seats. FLORIDA (17)

CARTER HAS ENJOYED a special relationship with Florida voters, winning, all three times his name has been on their ballot. But Cuban refugee problems, Jewish voters' doubts and Reagan's appeal to conservatives have made the president a slight underdog at this point. A Florida newspaper poll out today is expected to confirm private studies showing Reagan a few points ahead. Democrats say Carter has begun to solve some of his problems, by shifting refugee relocation operations to Puerto Rico and enlisting more help from Gov. Bob Graham's (D) organization. But the state remains a tough battleground for him.

Both parties have runoffs Tuesday for Senate nominations, with former state public service commissioner Paula Hawkins heavily favored over ex-Rep. Lou Frey Jr. for the GOP nomination and freshman Sen. Richard Stone in a very close contest with Insurance Commissioner Bill Gunter on the Democratic side. The November contest is also expected to be close.

Rep. Richard Kelly (R), indicated in Abscam, and Rep. Edward J. Stack (D) lost in the primaries, but it is uncertain which party will claim the seats. Fort Lauderdale Mayor Clay Shaw (R) is a strong threat to former State Rep. Alan S. Becker (D) in the Stack district. But attorney David Best (D) has a headstart on the Kelly seat, because Republicans must await Tuesday's runoff to know their nominee. GEORGIA (12)

OPTIMISTIC Republicans claim they can cut 10 points off Carter's 67-percent landslide of 1976 -- but that still makes him an easy home-state winner.

Sen. Herman E. Talmadge (D), denounced by the Senate for financial misconduct, divorced and treated for alcoholism, had to go through a primary and runoff for nomination to a fifth term. But he is running about 15 points ahead of former state Republican chairman Mack Mattingly and should come back to his Agriculture Committee chairmanship.

The only change expected in the House is the replacement of Dawson Mathis (D), who lost to Talmadge in the primary, by State Rep. Charles F. Hatcher (D). KENTUCKY (9)

THE STATE, WHICH CARTER won comfortably in 1976, is dead even in recent private polls -- something of a slip for Carter from earlier in September. Anderson's support is higher than in most states in this region. If Anderson declines, the Democratic tradition and the work now beginning by Gov. John Y. Brown's (D) organization could give Carter an edge.

Sen. Wendell H. Ford (D) is breezing to a second term over former state auditor Mary Louise Foust (R). No change is expected in the House lineup except that attorney Harold (Hal) Roger (R) will succeed retiring Rep. Tim Lee Carter (R). Louisiana (10)

PRIVATE POLLS in the last half of September showed the race dead even in a state Reagan has visited three times in two months. Carter, who has not yet been there, won Louisiana with a late visit in 1976 -- but this time Reagan's personal appeal is bolstered by growing Republicanism, symbolized by the 1979 victory of David C. Treen, the first GOP governor since Reconstruction.

Sen. Russell B. Long (D) and all but one of the House members won reelection in the September "open primary." The remaining contest pits two Democrats, Rep. Claude (Buddy) Leach and computer executive Buddy Roemer, in a country vs. city and conservative vs. liberal match. Leach was acquitted of vote-buying charges from his last election, but he still faces campaign finance violation counts that could weaken his position. MISSISSIPPI (7)

IT WAS VERY LATE election night in 1976 before Carter knew that an outpouring of black votes had given him a narrow (14,463-vote) victory here and cinched his election. It may be just as close this time. Carter retains black support and has the backing of Gov. William Winter (D) and the increasingly active Mississippi Association of Educators. But Reagan's appeal to conservative whites is probably greater than Ford's, and the Moral Majority is working on his behalf, aiding a well-financed Republican effort with plenty of volunteers. Democrats have increased their pad staff to 22 in a state where Carter now has a narrow lead but which he cannot take for granted.

There is no Senate race. Freshman Rep. Jon C. Hinson (R) shocked the state by disclosing in August two earlier incidents involving homosexual activities but denying he was a homosexual. The disclosure cost him some Republican financial backing but apparently has not crippled his campaign against Jackson attorney Britt R. Singletary (D), who must worry about significant black vote loss to Leslie B. McLemore, a Jackson State professor who is running as an independent. NORTH CAROLINA (13)

BENEFITTING FROM a close association with the Democratic Party organization of Gov. James B. Hunt Jr. (D), Carter has moved ahead here. A September poll by the Charlotte Observer had it Carter 46, Reagan 33, Anderson 6.

Hunt himself is a strong favorite to win a second term over State Sen. I. Beverly Lake Jr. (R).

Freshman Sen. Robert B. Morgan (D) is favored, but more seriously challenged by John P. East (R), a college professor and polio victim whose campaign -- like Reagan's -- is being directed and well financed on TV by the organization of Sen. Jesse Helms (R). East is trailing by 12-20 points in two polls, but has forced Morgan into lengthy defenses of his votes for the Panama Canal treaties and scrapping the B1 bomber.

The closest House races involve Democrats Lamar Gudger, Ike Andres and L. Richardson Preyer, but all of them -- particularly Gudger -- have survived squeakers before. OKLAHOMA (8)

WITH REAGAN, a runaway favorite (he led Carter by 3-to-1 margins in polls at the late-September state fair), the focus is on the choice of a successor to retiring Sen. Henry Bellmon (R). Andrew Coats (D), a former Oklahoma City district attorney, defeated a big name, Robert S. Kerr Jr. (D), for the nomination, and is a slight favorite over State Sen. Don Nickles (R) of Ponca City. Nickles, like Denton in Alabama, is a Roman Catholic with the backing of the Moral Majority, running in a state where Catholicism has been viewed as a political handicap. Nickles lacks a base in Tulsa or Oklahoma City, where Republicans normally have to find their votes, but he is clinging to Reagan's coattails. The presence of an anti-Carter Democrat from Oklahoma City, Charles Nesbit, a former attorney general running as an independent, could hurt Coats in his home base.

Dave McCurdy (D), a Norman lawyer, is slightly favored over Howard Rutledge (R) for the seat of retiring Rep. Tom Steed (D), but Rutledge, a retired Navy captain and much decorated Vietnam POW, has special appeal in a district with many military installations. SOUTH CAROLINA (8)

A RECENT Republican poll had Reagan even with Carter, but Democrats say the president has moved 5-6 points ahead since a September campaign visit. Carter ran strong here in 1976 and despite planned October visits by both Reagan and Bush and an effective GOP campaign, the "friends and neighbors" vote is expected to put the state in his column again.

An expected easy win for Sen. Ernest F. Hollings (D) over ex-State Rep. Marshall T. Mays (R) of Greenwood should help Carter. Charles D. (Pug) Ravenel (D), who lost for senator two years ago, is a very slight favorite over State Sen. Thomas F. Hartnett (R) to succeed retiring Rep. Mendel J. Davis (D). But Rep. John W. Jenrette Jr. (D), on trial on Abscam charges, is an underdog to Florence attorney John L. Napier (R) in an election that could be postponed if Jenrette is convicted and resigns. TENNESSEE (10)

THE CARTER-REAGAN contest looked very close in September polls; a leading Carter supporter called it a "dead heat" last week. But state observers think the momentum is in Carter's direction, in part because Sen. Howard H. Baker Jr. (R) is campaigning for GOP Senate candiates around the country and Gov. Lamar Alexander (R) is concentrating on his efforts to gain a legislative majority.

There is no Senate race, and no change is expected in the House delegation. TEXAS (26)

IT IS TOTAL WAR for Texas, which Carter won by 129,000 of 4 million votes last time and which looks just as close in the polls this time. The question is who votes. Republicans will invest $2.5 million in their sophisticated voter-identification program, which produced squeaker victories for governor and senator in 1978; Democrats are wrapping up a carefully targeted registration drive among blacks and Chicanos. Reagan's and Bush's personal popularity is pitted against a united Democratic effort in a state where party labels still count, but where Reagan may rate a razor-edge advantage.

In the House races, the most prominent is Majority Leader Jim Wright (D), but the most threatened incumbents are probably Jim Mattox (D), Ron Paul (R) and Bob Eckhardt (D). Democrats figure to replace retiring Reps. Ray Roberts (D) and Joe Wyatt (D) with former state Sens. Ralph Hall (D) and Bill Patman (D), but not without a struggle. VIRGINIA (12)

VIRGINIA WAS the only Southern state Carter lost in 1976, and Republicans assumed it would fall automatically to Reagan. Two September polls put Carter only 6 and 9 points back, but GOP strength and Democratic weakness (the Democrats have not elected a governor or senator in 14 years) make Reagan a clear favorite.

Republicans are sure to gain one House seat and could pick up two more. With conservative Democratic Rep. David Satterfield retiring, former Richmond mayor Thomas J. Bliley Jr. (R) is expected to crush John A. Mapp (D), a former night school dean.

Rep. Herbert E. Harris II (D) of Mount Vernon is a narrow favorite in his rematch with ex-Rep. Stan Parris (R), and Joseph L. Fisher (D) of Arlington faces another close race with his 1978 foe, attorney Frank R. Wolf (R).