Sen. Harry F. Byrd Jr.'s second and final decision to retire next January ends a drama that some said yesterday may have cost his die-hard supporters influence on Virginia politics.

By failing to resurrect a Byrd candidacy, the senator's allies only succeeded in strengthening the state's two political parties, some observers said, finally ridding both Democrats and Republicans of the lingering specter of the old Byrd organization.

"The effort fizzled, for whatever reason, and when something in politics fizzles, you lose credibility," said one top Republican. "We may be seeing the beginning of the end for these people."

The failure of the draft-Byrd movement also proved what was once unthinkable in Virginia: namely that all Byrds are not always invincible or above criticism.

By the time it was all over, the veteran senator had seen his judgment and record called into question by the state's major newspapers and heard top Republicans chastise him for even thinking of going back on his word. In the end, the Republicans, who had the most to lose if Byrd ran, were able to loosen Byrd's grip on their party by using his family tradition against him.

"The Byrd mystique is founded on integrity and consistency and the Republicans made it clear they were going to go after him on that," said Paul Goldman, a Democratic strategist. "They made it clear he would pay a historic price" if he changed his mind.

"When we were in Richmond at the GOP convention there was an awful lot of concern about someone saying he was not going to run and then reconsidering after giving his word," said Fairfax Del. John H. Rust Jr. "I thought that was not at all characteristic of the Byrd family."

Of all the Byrd lieutenants, the one who suffered most in last week's events was former governor Mills E. Godwin, the Democrat-turned-Republican seen by many as the spiritual leader of the "coalition," as the group of old Byrd Democrats and key political financiers has come to be called.

All week, politicians argued that Byrd was going to get back in the race, basing that view on the assumption that Godwin would not be so public about a Byrd draft unless he believed the senator would run. "Mills Godwin is not likely to go on a fool's errand," said one Republican.

It was a view that the Democrats, eagerly contemplating a three-way race that would necessarily give their candidate an edge, clung to until the end. "I am surprised," said state Sen. Adelard L. (Abe) Brault (D-Fairfax) late Monday after hearing of Byrd's announcement. "I did not think that Mills Godwin would put his neck out unless he had some fairly good assurance he was going to run."

The link between Godwin and Byrd goes back to the days when the senator's father controlled all that went on in state politics. As a young state senator, Godwin sat next to "little Harry" in the legislature and together they helped Harry Sr., then in the U.S. Senate, orchestrate a policy of "massive resistance" to school integration.

In the 1970s, Godwin, like "Little Harry," left the Democratic Party. But while the senator straddled the fence as an independent, Godwin actually signed on with the Republicans, a partisan affiliation that evaporated last week at the prospect of a Byrd candidacy.

That lack of party loyalty infuriated many Virginia Republicans as they gathered in Richmond last weekend to nominate Rep. Paul S. Trible of Newport News as their candidate to succeed Byrd. It was all that party leaders could do to keep the rank-and-file from publicly asking Godwin to get out of the party.

With the collapse of the Byrd candidacy, Godwin has been left high and dry, said some observers. "I think it would be fair to say his position has been weakened," said one Republican. "Many Republicans now regard him as a fair-weather friend."

Godwin endorsed Trible yesterday, as did J. Smith Ferebee, Francis T. West and other members of the group that had been urging Byrd to run. Others, including former congressman Watkins Abbitt and state senator Elmon T. Gray, are likely to rejoin the Democrats and back the candidacy of Lt. Gov. Richard J. Davis, said former state party chairman William Thomas.

Some argued that the Byrd effort was, in fact, a last gasp of a type of organization politics that had existed in Virginia, under the leadership of Harry Sr., outside the confines of party politics.

Byrd's decision to retire from politics leaves the coalition without a symbol of its independent, bipartisan approach to politics. And their failure to rally the state and the senator around one last show of the old Byrd strength was, to some, a sign that the state had finally outgrown the cult of personality and passed into an era of two-party politics.

"[Byrd's] decision makes it clear that the two-party system now applies to everybody," said former governor Linwood Holton, who became in 1969 the first Republican elected to the office since reconstruction.