Ronald Reagan rolled to a landslide victory in the South Carolina primary tonight, dealing a severe blow to John B. Connally's hopes of making a political comback in the South, and increasing the pressure on former president Gerald R. Ford to enter the race.

Connally, a former Texas governor, easily wrestled second place from fellow Houstonian George Bush, Punching still another pin in Bush's once-soaring presidential balloon.

But Connally's failure to come within striking distance of Reagan in a state where he had invested considerable time and money led spokesmen for Reagan and Bush to declare that Connally's days as a presidential candidate are numbered.

With 99 percent of the 1,675 precincts reporting, Reagan had 54 percent of the vote, Connally 30 percent and Bush 15 percent. A handful of other candidates had the rest.

In Miami, a smiling Reagan and his wife, Nancy, met reporters early in the evening, when results showed him ahead by 2 to 1.

"I have been telling some of you that I'm cautiously optimistic," Reagan said. "Now I'm cautiously ecstatic."

Reagan was asked whether he thought George Bush should drop out of the presidential race. He refused to answer the question directly, but said, "It's a long reach for him now to regain Big Mo [momentum]."

Tommy Thomas, Reagan's Florida chairman, said that the South Carolina victory would be a big help to Reagan in Tuesday's Florida primary, and predicted that Reagan would win it.

Connally, with his wife, Nellie, at his side, met with supporters at 9:35 p.m., as a band gave a slow rendition of "Happy Days Are Here Again."

Connally said he had tried unsuccessfully to contact Reagan in Florida. "He is entitled to congratulations, and I wanted to extend them to him," Connally said. "I'm disappointed we didn't win. Of course I am."

Sen. Strom Thurmond (R-S.C.) and his wife, Nancy, accompanied the Connallys, and drew a loud ovation when Connally said they had done more than anyone else to help.

"We'll go to Houston in the morning and reassess this thing," Connally said.

In Miami tonight, Bush spoke philosophically about the fact that he was buried in the South Carolina voting.

"You do well in some, not so well in others," Bush said, adding that "Ronald Reagan won in South Carolina. I congradulate him. Now we set our sights on Florida."

Bush said he had no regrets about having the race in South Carolina, because his way was a "national candidacy." But, he added, "We campaigned in the state only 2 1/2 days, and spent much less money there than anyone else."

He said the South Carolina voting might have an effect on the results in Florida, but added, "I like what I feel in Florida. I like the vibrations in Florida."

Former president Ford has been dropping hints about entering the race since Reagan trounced Bush and other Republicans in the Feb. 26 New Hampshire primary. Bush weak showing tonight is likely to be interpreted by supporters of a Ford candidacy as evidence that Bush cannot stop Reagan, making Bush's performance in Florida on Tuesday that much more important.

The returns bore ill for both Connally and Bush. Connally, his campaign heavily in debt, has fared poorly in every test of the young presidential campaign, and has no immediate prospect of a strong showing in the upcoming southern primaries or the March 18 primary in Illinois.

Although Connally has avoided such speculation, his strategists have said he needed to finish at least a strong second, probably within 5 percentage points of Reagan, to be able to raise the money and attract the attention necessary to remain a major force in the contest.

For Bush, the results represented a continuation of the slide his campaign has gone into since he was defeated by Reagan by 2 to 1 in the New Hampshire primary Feb. 26.

"This has to help us in Florida," said the South Carolina Reagan chairman, Rep. Carroll Campbell. "George Bush has said he is going to challenge us in the South, and we've wiped him out."

More than 130,000 people voted in the first GOP presidential primary in the state's history. This was less than some had expected, perhaps because there were heavy rains throughout the state most of the day.

Bush did poorly in all regions and among all groups of voters surveyed by AP-NBC, raising questions about his ability to mount a challenge to Reagan in the Georgia and Alabama primaries Tuesday. He appears to be better situated in Florida, where a Florida newspaper's poll today reported him running neck-and-neck with Reagan.

The primary was the first in the South in the 1980 campaign, and its results are expected to have a psychological impact on primaries Tuesday in Alabama, Florida and Georgia.

Connally, who had finished no higher than fourth in previous tests had staked his hopes for a comback in the Palmetto State, and campaigned here 21 days, four times as much as any rival.

He also had the endorsement of Thurmond and former governor James B. Edwards, the state's two most popular Republicans, who campaigned tirelessly for him.

Campbell, Reagan's state chairmman, said Thurmond was the only reason Connally had fared as well as he did. "Strom Thurmond should be congratulated. Without Strom Thurmond the results would have been completely different," he said. "I think we have to remember he doesn't have a Strom Thurmmond in other states."

Voters surveyed by Associated Press and NBC as they left the polls lent some credence to that statement. The survey showed that Connally polled best in rural areas where Thurmond had campaigned at his side. Asked if they made their decision on whom to vote for "because of the position of political leaders," 13 percent of the Connally voters said yes. None of the Reagan or Bush voters gave that reply.

His major problem among South Carolina voters was that he wasn't conservative enough for their taste. Two-thirds of the voters surveyed at the polls identified themselves as conservatives, compared with one-third in similar surveys during the New Hampshire and Vermont primaries.

Although GOP leaders had encouraged Democrats and independents to take part in the primary, only one voter in 10 identified himself as a Democrat.

Reagan beat his rivals in all six of the state's congressional districts, thereby winning all 25 of the state's delegates to the national Republican convention next July in Detroit. Under party rules, actual delegates are picked separately in caucuses, but are bound to vote for Reagan for two ballots.

The Democrats are not holding a primary. They will vote at precinct caucuses next Saturday.

The race here was as volatile as contests in other parts of the country. Oddsmakers changed their predictions almost weekly. Up until mid-January it looked like South Carolina would privide Connally with a one-on-one showdown with Reagan. But then Bush, his popularity skyrocketing from an upset win in the Iowa caucuses, and Sen. Howard H. Baker Jr. (R-Tenn.), made last-minute decisions to enter the primary. (Baker dropped out of the race for the GOP nomination last Wednesday.)

Harry Dent, a southern strategist in the Nixon White House and a respected political operative, joined with Bush, and for a few weeks there were signs that Bush might pull off a big upset.

But then came Bush's defeat by Reagan in New Hampshire, and a vicious campaign to label the former CIA diretor, congressman and ambassador a "liberal" -- a kiss of death in this conservative state. Suddenly, Reagan was up, Bush down.

Connally, meanwhile, running as a get-tough conservative, launched a media blitz and a series of bus tours across the state, stopping in many small towns never before visited by a presidential candidate.

The race had two big imponderables. The first was turnout. No more than 35,000 persons had never previously voted in a Republican state primary in South Carolina. But in an effort to expand the party's base, GOP leaders openly invited Democrats and independents to participate.

The other imponderable was Strom Thurmond. The 76-year-old senator is revered here, and campaigned non-stop with Connally for weeks, introducing him at every stop as "a fellow southerner, a patriot and a great American."

Despite his showing here, Bush had early victories in Iowa, Puerto Rico, and Massachusetts upon which to fall back. Bush's South Carolina strategist Harry Dent, claimed that the former CIA director and U.N. ambassador had accomplished his chief objective in the state. "That was to get this down to a two-man race. To see Howard Baker and now John Connally out of the race, we've accomplished that."

But he acknowledged that Bush's umimpressive showing here would increase pressure on former president Ford to get into the race, something he said, that "might hand the nomination to Ronald Reagan."

Reagan relied heavily on a base of support among hard-core conservatives to roll up large margins across the state, and the only region he was in danager of losing with the PeeDee area in the northeast corner of the state.

Reagan and Connally both benefited from better organizations than Bush and an increase in momentum in the closing weeks of the campaign. Connally was gaining on Reagan in the last days of the campaign. Half of the people who made up their minds in the last week voted for him.

Half of the voters polled by AP-NBC said they'd been contacted by Connally and Reagan. One in eight had been contacted by Bush forces.

The survey showed little correlation with returns in recent weeks in New Hampshire and Massachusetts, Half of those surveyed had made up their minds whom to vote for a month ago. Of those, Reagan got two of every three voters.

Apparently none of the candidates was sucessful in attracting black voters. If the Greenview precinct in Columbia was an indication, few blacks participated. A moderate income neighborhood in which all but eight 1,734 registered voters are black, only two votes had been cast at Greenview by 5 p.m. The two white pollworkers spent most of the day reading books they had brought along.