Following is a state-by-state roundup of the South (numbers in parentheses are Electoral College votes): Alabama (9)

As elsewhere in the South, President Reagan's strength among white voters is so overwhelming that Democratic presidential nominee Walter F. Mondale has not been able to make it a close race here, despite backing from black leaders, teachers and a union movement stronger here than in most other Dixie states.

Reagan coattails are questionable, however. Sen. Howell Heflin (D) is far ahead in his race for election to a second term over ex-representative Albert Lee Smith Jr. (R). Freshman Rep. Ben Erdreich (D) of Birmingham, who beat Smith in 1982, is favored to hold off the challenge of former state representative J.T. (Jabo) Waggoner (R), a Democrat-turned-Republican. In the Mobile district of retiring Rep. Jack Edwards (R), another convert, former state senator H.L. Callahan is struggling, despite the popularity of Reagan and Edwards, to hold off the challenge of attorney Frank McRight (D). Arkansas (6)

Reagan was in good shape, by all polls, before he stopped in Little Rock last Friday to try to spread his coattails for Rep. Ed Bethune (R), challenging Democratic Sen. David Pryor's second-term bid, and state Rep. Judy Petty (R), opposing Pulaski County Sheriff Tommy Robinson (D) for Bethune's House seat. Polls show Reagan nearly 20 points ahead of Mondale, but Pryor is as far ahead of Bethune. Each time the challenger accuses him of opposing Reagan, the folksy incumbent turns up with a television ad explaining he just can't back an administration that "even asked a widow with one arm to get a job."

Petty, an outspoken conservative and breakneck campaigner, is up against a legend in Robinson, whose law-and-order policies extend to chaining prisoners to guard towers when cells are full. Borrowing heavily, Robinson is outspending his rival in the close race, and when Reagan came to town, Robinson welcomed him with a full-page newspaper ad promising, "When you're right, I will support you 100 percent . . . . "

Standing aside from all this, Gov. Bill Clinton (D), who was upset for reelection in 1980 and came back in 1982, is comfortably out in front of Woody Freeman (R), a contractor and political newcomer. Florida (21)

Despite the seventh-largest bloc of electoral votes, Florida has been ignored by the candidates. The reason: an early, overwhelming Reagan lead, which held at 60 to 33 percent in the latest Washington Post-ABC poll and a slightly higher percentage in a poll by three state newspapers. Exploiting Reagan's popularity, Republicans signed up three new voters for every two the Democrats enrolled, but Democrats still have 1.4 million more registered voters.

Reagan's numbers create coattail problems for Rep. Daniel A. Mica (D), facing college president Don Ross (R), and Rep. Larry Smith (D), who is opposed by former state representative Tom Bush (R). But the only certain GOP gain is the expected reelection of Rep. Andy Ireland, a fourth-termer who switched parties. Georgia (12)

Mondale has the Jimmy Carter connection and the vote-turnout machine of Atlanta Mayor Andrew Young going for him, but after the Bert Lance affair, most of the top Democratic leaders have gone fishing.

Gov. Joe Frank Harris (D) appeared with Mondale early in the campaign, and then with Bush. Lt. Gov. Zell Miller (D) said, "I am going to vote for Walter Mondale. I'll help him in my limited way, but my enthusiasm gas tank is on empty. In fact, I'm sniffing, and I can't even smell the fumes." Reagan leads by 12-to-20 percentage points in various polls. Sen. Sam Nunn (D) has only token opposition from teacher Jon Michael Hicks (R). Kentucky (9)

Mondale's strong showing in the Louisville debate with Reagan gave a lift to the campaign organized for him by Sen. Wendell Ford (D), but private polls in both parties still show Reagan up by more than 15 points.

All year, Sen. Walter D. Huddleston (D) has denied persistent reports that his third-term bid could be upset by the aggressive challenge from Jefferson County Judge Mitch McConnell (R), but his backers are no longer denying their nervousness. Reagan coattails, the incumbent's "softness" of support, and Reagan ads plugging McConnell on the tax issue have eroded much of Huddleston's lead.

State Rep. Carl C. (Chris) Perkins (D), namesake son of the 18-term incumbent who died last August, is almost certain to defeat businessman Aubrey Russell (R) for his father's House seat. Louisiana (10)

Voting in Louisiana Tuesday will be strictly a matter of conscience. Reagan has held leads of 2-to-1 over Mondale in polls all fall, and Sen. J. Bennett Johnston (D) and the eight incumbent representatives -- six Democrats and two Republicans -- were all reelected by getting more than 50 percent of the votes in the Sept. 29 nonpartisan primary. Mississippi (7)

Even with a good turnout and 90 percent of the black vote, Mondale needs almost one of three white votes to win. Polls show Reagan is holding him well below that figure and running comfortably ahead in the state. So is Sen. Thad Cochran (R) in his second-term contest with ex-governor William F. Winter (D). Cochran appears likely to draw one-fifth of the black vote, probably the best for any major GOP candidate in the South.

Redistricting has boosted the black percentage in the 2nd Congressional District, and Democrats lately have begun to think there may be enough of a turnout operation for state Rep. Robert G. Clark (D), the grandson of a slave, to give him a chance in his rematch with freshman Rep. Webb Franklin (R). It rates a tossup. North Carolina (13)

Despite a Reagan lead that has been measured at 20-to-25 points, the Tar Heel State has more close, hard-fought contests than any other in the country. The landmark Senate contest between Sen. Jesse Helms (R) and Gov. James B. Hunt Jr. (D) has been tipping back and forth within a narrow range for months, but late last week the trend in private polls was clearly toward Helms. A Gallup Poll for several news organizations today showed Helms leading Hunt 49 to 46 percent. Democrats hope Hunt can win it on organization.

The same Gallup Poll shows Rep. James G. Martin (R) has overcome Attorney General Rufus Edmisten's (D) early lead in the race for governor and now leads 49 to 44 percent.

Republicans think they will defeat two Democrats in the House and, with breaks, could get more. Rep. Ike Andrews (D) is in a rematch with William Cobey (R), former athletic director at the University of North Carolina and a Helms protege, who has a better organization than the one that came very close in 1982. In another rematch, freshman Rep. James McClure Clarke (D) faces ex-representative William M. Hendon (R), who lost by 1,325 votes without the long coattails Reagan will provide.

Other possibly vulnerable Democrats are freshman Rep. Robin Britt (D) facing moderate state Rep. Howard Coble (R), and, at lesser risk, Reps. Stephen L. Neal (D) and W.G. (Bill) Hefner (D), who each have 10 years' seniority. Their opponents have tied themselves to Helms.

With all this, Democrats have an even chance of winning Republican gubernatorial candidate Martin's Charlotte House seat, where attorney D.G. Martin (D), no relative, has a name-recognition advantage over businessman J. Alex McMillan (R). Oklahoma (8)

It's name-your-margin time at the top of the ticket, with Reagan cruising over Mondale and Sen. David L. Boren (D) leading in his second-term race by a mile over token opponent Will E. Crozier (R).

House Budget Committee Chairman James R. Jones (D) has used his incumbency and a big campaign treasury to blunt the effort of former U.S. attorney Frank Keating (R) to ride Reagan's coattails to victory. South Carolina (8)

South Carolina had two candidates for the Democratic presidential nomination, Sen. Ernest F. Hollings and Greenville native Jesse L. Jackson. Both have been stumping for Mondale, but the latest Post-ABC poll confirms the widespread belief that Reagan will win with something like the 60 percent vote last week's Greenville News poll gave him. Sen. Strom Thurmond (R), going strong at 81, is headed for a sixth term over little-known minister Melvin Purvis Jr. (D). Tennessee (11)

Reagan had only a 4,710-vote plurality here in 1980, and the latest Post-ABC poll and other surveys show that although he is in front, his margin is significantly smaller than in the states further south.

The big story in Tennessee this year is the expected victory of 36-year-old Rep. Albert Gore Jr. (D) for the seat being vacated by retiring Senate Majority Leader Howard H. Baker Jr. (R). Gore is swamping his opponent, former state senator Victor Ashe (R), and keeping such a distance from the national ticket that at one point Ashe offered $5 to charity if Gore would mention Mondale's name in their debate. He didn't.

Despite a heavily publicized paternity suit, former Democratic state chairman Bart Gordon (D) is favored to win Gore's old House seat over businessman Joe Simpkins (R). Texas (29)

Even with a huge registration increase and a Mondale visit today, Democrats have been counting the state in Reagan's corner since Mondale spurned Sen. Lloyd M. Bentsen (D) as his running mate. The latest Post-ABC poll gives Reagan a 58-to-36 percent lead.

In the race to succeed retiring Sen. John G. Tower (R), Rep. Phil Gramm (R), the supply-side economist who switched parties after House Democrats disciplined him for backing the Reagan budget and tax bills, is out in front of liberal state Sen. Lloyd Doggett (D) in their bitter battle. The Post-ABC poll gave Gramm a 51-to-40 lead.

Democrats expect to win Gramm's old House seat, traditionally Democratic territory where former state representative Dan Kubiak (D) is better known than his engineer opponent, Joe Barton (R). Another open seat, vacated by Rep. Kent Hance (D) when he tried for the Senate nomination, seems likely to go Republican, with Larry Combest (R), a former Tower aide, favored over Hance's former assistant, Don R. Richards (D).

Two Democratic incumbents face serious coattail problems: Freshman Rep. Tom Vandergriff (D), the former mayor of Arlington, is up against economics professor Richard Armey (R), who stirred up a storm by proposing a phase-out of Social Security. Five-term Rep. Jack Hightower (D) has at least as serious a problem against attorney Beau Boulter (R) in the Panhandle.

State Rep. Tom DeLay (R) is a cinch to succeed Rep. Ron Paul (R), who tried for the Senate nomination, and Bexar County Judge Albert G. Bustamante (D) has been considered a shoo-in ever since he defeated Rep. Abraham Kazen Jr. (D) in the primary. Virginia (12)

Reagan's big lead in the Old Dominion is no news; the only Democrat to win it in 36 years was Democratic Gov. Charles S. Robb's father-in-law, President Lyndon B. Johnson. Sen. John W. Warner (R), who won a squeaker for his first term in 1978, has had an easy time with liberal former state delegate Edythe C. Harrison (D), outspent 6 to 1 and complaining of a lack of support from Robb and the Democratic establishment.

Despite the top-the-ticket GOP strength, Democrats are favored to hold their four House seats and are threats in two of the six Republican districts. Freshman Rep. Herbert H. Bateman (R) of Newport News has been pressed hard by John McGlennon (D), a William and Mary political science professor. In the Shenandoah Valley seat being vacated by Rep. J. Kenneth Robinson (R), former state delegate D. French Slaughter (R) has the advantage of a Republican voting tradition against attorney Lewis M. Costello (D), a Robb ally.

Freshman Reps. James R. Olin (D) and Frederick C. Boucher (D), who had the tiniest of margins in 1982, are expected to have slightly easier bouts with their new rivals, respectively, former state senator Ray Garland (R) and state Del. Jefferson Stafford (R).