ASHINGTON - With all hope lost of foiling Patrick J. Buchanan's flight from the Republican fold, GOP leaders are plotting ways to ruin the conservative firebrand's renegade run for the Reform Party's presidential nomination.
The showdown begins today, when Buchanan, one of the GOP's fiercest ideological warriors, is scheduled to announce he will forsake his lifelong bond with the party of Lincoln and Reagan for the Reform movement of Texas billionaire H. Ross Perot and Minnesota Governor Jesse Ventura.
Republican strategists said stopping Buchanan before he can win the Reform Party nomination and gain enough strength to secure a potentially pivotal spot next year in the presidential debates ranks among their top priorities.
But GOP planners are split on how best to counter Buchanan's defection: ignore him, besiege him, or wage a less incendiary counterattack as they wait to see if the former television commentator's campaign is undercut by Perot, developer Donald J. Trump, or another Reform hopeful.
The stakes are high, as Buchanan prepares to pursue the Reform Party's $13 million in federal matching funds and try to cut support for the GOP nominee - and possibly the Democratic candidate - with his ''America First'' appeal to conservative voters.
To many GOP strategists, he is the Benedict Arnold of modern Republican politics. And fearing a replay of 1992, when Perot took 19 percent of the presidential vote and stymied President Bush's reelection effort, many Republican insiders believe there is no better time than now to launch an all-out assault against Buchanan.
''I take Buchanan deserting the party as a total act of war,'' said Rich Bond, former chairman of the Republican National Committee. ''I will do everything in my power to raise his negatives, using his own words and actions against him.''
Several GOP operatives said party leaders are wrestling with how much they should actively try to savage Buchanan, who has opened himself to intense scrutiny on several fronts. Most notably, he has been forced to defend himself against the perception that he is soft on Adolf Hitler, architect of World War II and the Nazi Holocaust.
Bond embodies the GOP sector that wants to fully exploit such controversy. ''Buchanan has alienated so many groups of Americans that all he has left is some white men,'' Bond said. ''The only way he could make things worse is if he makes David Duke his running mate,'' Bond added, referring to the former Ku Klux Klan leader from Louisiana.
But some Republican strategists said they believe the best response to Buchanan's defection is none at all.
''I just think Pat Buchanan is a figment of his own imagination,'' said Eddie Mahe, a prominent GOP consultant. ''It's best to ignore him, do nothing to make him any bigger than he is. Just wave goodbye to him and cross him off the list.''
Mahe also cited Buchanan's media savvy, honed as an adviser to Presidents Nixon and Reagan, and as a longtime television commentator. ''You pay him any attention,'' Mahe said, ''and he will use it to his advantage.''
Buchanan, who has not granted interviews in the final days before his announcement, recently described his pending move to the Reform Party as a source of ''mortal terror'' for the Washington establishment.
But he acknowledged that faring well in the 2000 election could hinge on whether he is allowed to participate in nationally televised debates with the two major party nominees. Perot was barred from the 1996 debates between President Clinton and former Senate majority leader Bob Dole, which his supporters largely blame for his disappointing 8-percent finish.
''If I get into the race, my determination will be to get into the debates,'' Buchanan said at a recent book party in Washington. ''And if I get into a freewheeling forum, I think I can become the president of the United States, because I think it is a volatile election and I think voters would see an agenda that is new and different'' from the Democratic and Republican platforms.
At the very least, Republican Party officials said, they will continue to hammer Buchanan as an ego-driven turncoat whose desertion could cost the GOP nominee the White House and the possible opportunity to create a solid, conservative majority on the Supreme Court if one or more justices retire.
A nationwide poll released Friday showed 40 percent of Republican voters believe Buchanan's bolt to the Reform Party would damage the GOP. Only 16 percent thought Buchanan's departure would benefit the Republican Party, according to the survey by Marist College's Institute for Public Opinion.
A GOP official said party leaders at least will continue to invoke Reagan, who argued that third parties traditionally ensure the election of the candidates they most opposed.
''Beyond making points like that, we haven't straightened out how else we will respond,'' said a GOP official who asked not be identified. ''Some of us believe we shouldn't engage Buchanan or go after him directly because it would only draw more attention to him.''
Buchanan is fleeing the GOP after an abysmal showing in the Iowa straw poll in August, a year of lackluster fund-raising, and a steady diet of polls that reveal little public appetite for his candidacy on the Republican ticket.
Yet his theme of protecting the nation's borders and jobs appeals to many voters, and he has demonstrated some drawing power at the polls by finishing a strong second to President Bush in the 1992 New Hampshire primary, and beating Dole in the 1996 primary there.
After his announcement this morning in a Virginia suburb of Washington, Buchanan will speak tonight in Manchester, N.H., tomorrow in Detroit, and Wednesday in South Carolina.
Later in the week, Buchanan plans to visit North Dakota and Minnesota, where, an aide said, he hopes to pay a courtesy call on Ventura. Calling Buchanan a ''retread,'' Ventura recently urged Trump to seek the Reform Party nomination, an invitation Trump is actively weighing.
