Presidential contenders Ronald Reagan and John Connally charged into the ranks of 2500 Virginia Republicans here this weekend, and it was Connally who clearly piqued the interest of many heretofore neutral politicians, and some longtime Reagan supporters.

Although no one suggested that Reagan - considered the Republican frontrunner in Virginia and around the nation - had lost his position as the favored candidate in the Old Dominion, Connally's foreceful campaign style dazzled what was otherwise often a lackluster GOP State Convention.

"He got a terrific reception, and his supreme confidence really almost astonished people," said Virginia Attorney General J. Marshall Coleman of the former Texas governor's appearance at a reception Friday evening.

Calling Connally "quick study," Coleman, who thus far has no presidential preference, described Connally's impact on a crowd of more than 1,000 as "almost Rooseveltian . . . he had them in the palm of his hand."

Reagan, who was the presidential choice of most of Virginia's 51 delegates to the 1976 GOP convention, also brought the crowd to its feet for an enthusiastic ovation late tonight as he concluded his keynote banquet address.

Introduced with the query -" Is it going to be Rome or Reagan?" - the former California governor peppered the audience with one-liners attacking federal waste and the high cost of government.

"A government program once launched is the nearest thing to eternal life you'll ever see on this earth," said Reagan, whose speech was nevertheless much more restrained than Connally's earlier remarks.

Reagan urged Virginia Republicans to continue with their string of election successes in local, legislative and state-wide offices.

"What you did was an inspiration to Republicans all over the nation," Reagan told the crowd. He said he hoped Republicans would increase their numbers in all states just as he said his own was trying to do.

The GOP presidential nomination showdown is a year away, but the presence of many of the aspirants in that contest was easily the biggest attraction in this southwestern Virginia city. Making separate appearances at what is the first off-year GOP convention in the state's history were not only Reagan and Connally but also Rep. Philip Crana (R-ILl.), and family or political stand-ins for Sen. Howard Baker (R-Tenn.), Sen. Robert Dole (R-Kan.) and former National Party Chairman George Bush.

But the gathering also served as a kind of "pep rally" for Virginia republicans who hope to add to their considerable stage-wide election gains by increasing their numbers in local and state legislative offices as well.

"This started out as a kind of showcase for presidential candiates but I think a sidelight has been the showcase for legislative candidates," said State Sen. Wiley Mitchell (R-Alexandria). He said that the upcoming state House of Delegates contests this fall have drawn the largest and most qualified collection of Republican contestants ever.

Zeroing in on expected state House gains, Mitchell and other GOP incumbents hosted a seminar for about 60 legislative candidates who are challenging longtimed incumbent Democrats. The purpose, he said, was to explain the lawmaking process in Richmond "so their opponents don't make them look like idiots."

Connally, Reagan and Crane held separate news conferences while the convention was under way. Each carefully avoided attacking one another and instead directed their campaign assaults on the Democratically controlled Congress and on Jimmy Carter, blaming them for inflation, the gasoline crisis and - in the case of Reagan and Connally - an influx of too many imported Toyota cars from Japan.

Calling himself the most qualified presidential candidate in this century Connally did not hesitate a second when asked if he would campaign against Virginia Lt. Gov. Charles Robb should the son-in-law of his old friend Lyndon Johnson become a gubernatorial candidate.

"Unless he switches parties, I sure will," Connally promised.

Reagan, in marked, soft-spoken contrast to Connally's fiery speechmaking, talked more generally about the expectation of further Republican victores in Virginia.

"I know that a great many Democrats in Virginia think like Republicans," he said.

Connally was squired around the convention by former governor Mills E. Godwin - like Connally and Reagan, a Democrat turned Republican. Reagan has Rep. Paul Trible (R-Va.) and Helen Obenshain, the window of Richard Obenshain, cochiring his Virginia campaign.

With the Virginia GOP choosing up sides already, their meeting this weekend took on the trappings of a nominating convention even though the party itself had virtually nothing of importance on its Roanoke agenda.

"Everybody realizes that there's no business to be done here," said Attorney General Coleman, who suggested that the Republican delegates had really come to the convention to see and mingle with all the Republican presidential hopefuls.