The solid southern base that caried Jimmy Carter to the White House four years ago crumbled last night as Ronald Reagan swept to victory in several key states.

The president was a clear winner only in his home state of Georgia. He was in a tight race with Reagan in Arkansas, and appeared to have carried North Carolina. Reagan won the big electoral states of Texas and Florida as well Oklahoma, Alabama, Mississippi, Kentucky, Louisiana, South Carolina and Virginia, and was leading in Tennessee.

In 1976, Carter carried 127 of the 147 electoral votes in the 13 southern states, losing only Virginia and Oklahoma to Gerald R. Ford. Senior Reagan adviser James Baker said: "We're surprised we went into the South and blew him away."

The Republicans also appeared to be picking up two Senate seats in the South, in Alabama and Florida, and had a shot at a third in North Carolina. Jeremiah Denton, a former Vietnam prisoner of war, was leading Democrat Jim Folsom Jr. in the race to take the seat of defeated incumbent Donald Stewart in Alabama. And Paula Hawkins held a slight lead over Democrat Bill Gunter in Florida for the seat of incumbent Richard Stone. Republican John P. East had a slim lead over incumbent Robert Morgan in North Carolina.

The GOP also retained the seat of retiring Sen. Henry L. Bellmon in Oklahoma, as 31-year-old businessman Don Nickles defeated Democrat Andy Coats. Incumbent Democrats who won included Wendell Ford of Kentucky and Ernest (Fritz) Hollings of South Carolina. Herman E. Talmadge of Georgia, another incumbent Democrat, had a narrowing lead over Republican Mack Mattingly.

Incumbent Democratic Gov. James Hunt Jr. was reelected in North Carolina, but Arkansas Gov. Bill Clinton was trailing slightly behind Republican Frank D. White.

In notable House races in the region, House Majority Leader Jim Wright won easily in Texas, but Rep. Bob Eckhardt, another powerful Democrat, was trailing Republican Jack Fields, and Rep. Richardson Preyer clung to only a slight lead in a close North Carolina House race. In South Carolina convicted Abscam defendent John W. Jenrette Jr. appeared to have lost to Republican John Napier. Alabama

President Carter's efforts to win support among blacks, rural whites and blue-collar voters in Alabama appeared to have fallen short last night. Reagan held a slight lead, with 85 percent of the vote counted.

Adm. Jeremiah Denton, 56, the Vietnam prisoner-of-war hero from Mobile, became the first Republican elected to the Senate from Alabama since Recontruction. He defeated Public Service Commissioner Jim Folsom, 31, son of a two-term Alabama governor whose "magic" family name was insufficient to stunt Denton's appeal to patriotism and high moral values.

With 80 percent of the vote counted, Denton held a 4-point lead. In House races, Birmingham insurance man Albert Lee Smith, a former John Birch Society member, defeated City Councilman W. B. (Pete) Clifford (D), a conservative Methodist minister, upset Rep. John Buchanan (r) in the primary. Arkansas

Carter and Reagan were neck-and-neck in Arkansas early this morning. The president easily won the state with 65 percent of the vote four years ago. t

Incumbent Democratic Sen. Dale Bumpers was winning his campaign for reelection, but Gov. Bill Clinton, a former Rhodes scholar who already has been mentioned as a future presidential candidate, was locked in a close race with Republican challenger Frank D. White.

There was no chance in the state's House delegation, with each party retaining its two seats. Florida

Florida, with its 17 electoral votes, was widely expected to line up for Reagan and he took the state handily.

With more than 80 percent of the votes counted, the Republican president-elect was capturing 55 percent of the vote, compared with slightly under 40 percent for Carter.

Independent party candidate John B. Anderson was pulling in 5 percent of the vote, and Liberation Party candidate Ed Clark, about 1 percent.

The U.S. Senate race was still undecided early this morning. The favorite, Republican candidate Paula Hawkins, head of the state's Public Service Commission, was running ahead of state insurance commissioner Bill Gunter (D), but only by about 51 percent to Gunter's 49.

The Republicans won a House seat in Fort Lauderdale, where Mayor Clay Shaw defeated the Democratic candidate, Alan S. Becker, a former Dade County legislator. Becker had ousted incumbent Rep. Edward J. Stack (D) in the September primaries. Across the state, Republican Bill McCollum was maintaining a narrow lead over David Best (D) for the seat now held by Rep. Richard Kelly (R), who was indicted the FBI's Abscam investigation. Georgia

President Carter easily carried his home state of Georgia yesterday. With 80 percent of the vote counted, Carter was leading Reagan by almost a 2-to-1 margin.

Sen. Herman E. Talmadge (d), 67, defeated Republican challenger Mack Mattingly, ex-chairman of the state Republican Party, to win his fifth term in a Senate which rebuked him 14 months ago. With 80 percent of the precincts counted. Talmadge was expected to hold onto his narrowing 11-9 lead over Mattingly. Still, with Atlanta's anti-Talmadge strongholds still out, Mattingly had yet to concede and Talmadge had yet to claim a victory.

A story of political resurrection, Talmadge survived a primary runoff that featured his 1979 Senate denouncement for financial misconduct and his bitter divorce.

All nine incumbents won reelection to the U.S. House. State Rep. Charles F. Hatcher (D) will replace Rep. Dawson Mathis (D), who lost to Talmadge in the Senate primary. Kentucky

Ronald Reagan took Kentucky's nine electoral votes with a narrow 16,000-vote victory over the president by rolling up impressive margins in the Louisville suburbs and traditionally Republican southeastern Kentucky.

As expected, Carter took the black vote in the cities, but Reagan cut into his margins in the usually Democratic regions of Western Kentucky.

Incumbent Democratic Sen. Wendell Ford easily won reelection over GOP challenger Mary Louise Foust. And there was no change in the House delegation, with all the incumbents winning and Republican Harold (Hal) Rogers restraining the seat of retiring Rep. Tim Lee Carter for the GOP. Louisiana

Louisiana, one of the South's main battlegrounds, handed Ronald Reagan a runaway victory over President Carter yesterday.

With more than 80 percent of the state's precincts reporting, the voters were giving Reagan a plurality of about 73,000, which was approximately the same as Carter's margin over Gerald R. Ford in 1976.

The only congressional seat in contention was that of Rep. Claude (Buddy) Leach (D) in northwest Louisiana. He was crushed by another Democrat, computer executive Buddy Roemer, under the state's unconventional nonpartisan election system for members of Congress. Mississippi

Mississippi, the Deep South state that put Jimmy Carter over the top in 1976, gave its seven electoral votes to Ronald Reagan last night. With 80 percent of the vote counted, he was holding a slim but solid 2-point lead over Carter.

All five incumbent congressmen were reelected.

The conservative politics of Rep. Jon C. Hinson (R), 35, helped save his seat as he defeated Britt R. Singletary (D), 30, a Jackson attorney and black independent Leslie McLemore, a political science professor. In a surprise disclosure last summer, Hinson told a news conference that he survived a fatal fire at a Washington movie theater frequented by homosexuals. "These have been the worst three months of my life," he said last night.

Rep. Jamie Whitten, powerful chairman of the House Appropriations Committee, who has spent 40 years in Congress, fought off an assault by T. K. Moffett, 31, an attorney backed by the Moral Majority, to win another term. North Carolina

Reagan appeared to have captured North Carolina, while incumbent Democratic Gov. James B. Hunt, Jr. coasted to a second term.

Hunt won a landslide victory over State Sen. I. Beverly Lake Jr.

The Senate race was also extremely tight, with incumbent Democrat Robert Morgan hanging on to a 1-point lead over his Republican challenger, John P. East, a political science professor and protege of Sen. Jesse A. Helms (R).

In House races, six-term Rep. Richardson Preyer (D) of Greensboro appeared to be in serious trouble. With about 25 percent of the votes in that district race counted, Republican challenger Eugene Johnston had built up a lead of more than 10 points over the veteran Preyer.

In another hard-fought congressional contest, Rep. Lamar Gudger (D) was running slightly behind Asheville businessman William M. Hendon (R) with less than half of the votes counted. Oklahoma

Reagan rolled up an impressive 60-35 percent margin in Oklahoma last night and carried a new Republican senator along with him. Don Nickles, a 31-year-old businessman who had the backing of the Moral Majority, had a 53-47 lead over former Oklahoma City prosecutor Andy Coats in the race fill the seat of retiring Republican Sen. Henry L. Bellmon.

Democrat Dave McCurdy won the House seat of retiring Rep. Tom Steed over former Vietnam prisoner of war Howard Rutledge. The other House incumbents held their seats. South Carolina

South Carolina, a heavily Democratic state that defected from the party in 1964 for Barry M. Goldwater, and in 1968 and 1972 for Richard M. Nixon, defected again yesterday to give its eight electoral votes to Ronald Reagan.

In 1976, President Carter captured the state by appealing to its Democratic heritage and his red clay roots. This year, black voters and the backing of Gov. Dick Riley were not enough.

Sen. Ernest F. Hollings won a landslide victory over former state representative Marshall T. Mays (R). Republicans appeared on the verge of capturing a majority of the congressional delegation for the first time since Reconstruction. With more than half the vote counted, attorney and ex-Strom Thurmond aide John L. Napier held a 10-point lead over Rep. John W. Jenrette Jr. (D), plagued by his Abscam conviction. And state Sen. Thomas F. Hartnett (R) was holding onto a narrow edge over Charles D. (Pug) Ravenel (D) for the seat of retiring Democratic Rep. Mendel J. Davis.

Incumbent Republicans Carroll Campbell and Floyd Spence won reelection to the U.S. House, as did incumbent Democrats Butler Derrick and Ken Holland. Tennessee

Tennessee was one of Carter's strongest states in 1976, but Reagan captured it yesterday by a razor-thin margin.

With 99 percent of the vote counted, the former California governor was leading the president by more than 5,000 votes. The state had been expected to stand fast for Carter.

No change was expected in Tennessee's congressional delegation. Texas

In what appeared to be a record vote in Texas, Reagan won by a large margin over the president. The Republican organization turned out such a huge vote in suburban areas that some voters had to wait in line for three hours to cast their ballots. GOP Gov. Bill Clements said that 43,000 volunteers were behind the effort.

Carter coordinator Bob Beckel claimed the president held onto the massive Hispanic vote he needed, but acknowledged his campaign couldn't overcome the GOP suburban vote.

House Majority Leader Jim Wright won his race easily, but Rep. Bob Eckhardt was in a race too close to call with Republican challenger Jack Fields, and another Democratic incumbent, Rep. Jim Mattox, was trailing Tom Pauken. Incumbent Republican Rep. Ron Paul was neck and neck in a race with Democrat Mike Andrews, and Democrat Ralph Hall was leading in the contest to succeed retiring Democrat Ray Roberts. William Patman, son of the late Rep. Wright Patman, was winning the seat of retiring Democrat Joe Wyatt.