Even as Rudy Giuliani emerges from his campaign’s first real rough patch, a number of conservative Catholic organizations are in the process of rolling out potentially broad-reaching “viral” initiatives with the common aim of denying him the Republican nomination.

A conservative Catholic P.A.C based in a key swing state is planning an anti-Giuliani “multimedia effort” for a June debut. A national network of politically savvy Catholic activists is creating a heavy-hitting Web site—patterned after the controversial Catholics Against Kerry effort in 2004—scheduled to appear around the same time. And earlier this month, a disabled vet working out of his home in Blytheville, Ark., launched an invitation-only “Stop Rudy” social-networking site, where Giuliani-haters from across the nation have begun to meet and coordinate real-world planning from behind the protection of a members-only log-in.

“We’re not going to hide,” said Joseph Cella, executive director of the conservative Catholic advocacy group Fidelis. “We just want to influence the conversation.”

The emergence of the groups at this point in the campaign seems to have been motivated in equal parts by Mr. Giuliani’s worst moment as a Presidential candidate and his best. His painfully equivocal answer to a question about Roe v. Wade at a May 3 Republican debate angered them. His subsequent dramatic recovery at the next debate on May 15—at which the former Mayor turned in a winningly aggressive performance on the subject of Sept. 11—scared them into action.

Fidelis America, the political-action committee of Fidelis, is arguably the best-established of the anti-Rudy organizations, and it’s certainly the most open about its overall strategy. A Michigan-based Catholic organization cleverly designed to navigate the tangle of federal campaign-spending restrictions, the group’s various arms have been registered as political-action committees, independent-expenditure committees and nonprofits.

The organization, whose executive director previously headed the Ave Maria List, a nonprofit political entity founded by Domino’s Pizza magnate Thomas Monaghan, is perhaps best known for alleging bias when CNN refused to run one of their issue ads featuring Mother Teresa, but later ran a spot by the pro-choice group NARAL. Fidelis promptly launched an e-mail campaign that crashed the network’s servers within hours.

Fidelis also claims credit for spearheading the development of WithdrawMiers.org, a site that registered more than two million hits during the ideologically moderate former White House counsel’s failed bid for a Supreme Court slot.

Mr. Cella says that the organization will try to provide a comprehensive, Web-based “clearinghouse” of issue-based opposition research, and that it will also engage in the distribution of more traditional negative literature, as when the group recruited a handful of volunteers to network and pass out its anti-Rudy materials at the South Carolina debate earlier this month.

“More is afoot—not just from us, but others,” said Mr. Cella, who has also served as an editor at the popular conservative Web site Redstate.com. “It will be edgy. Creative. Hard-hitting.”

A separate effort from another group of Catholic activists—to operate under the admirably straightforward title of Catholics Against Rudy—will also take aim at Mr. Giuliani’s record on social issues. It’s the brainchild of Georgia lawyer Steve Dillard, best known as the formerly anonymous voice of Southern Appeal, a conservative Catholic legal blog that drew a wide-ranging, fiercely loyal audience until Mr. Dillard outed himself and subsequently retired the site five months ago.

Mr. Dillard, along with other bloggers, commentators and activists who are planning to participate in the effort, are modeling their project on the headline-grabbing Catholics Against Kerry site that targeted the Democratic nominee three years ago. (Organizers say that none of the individuals involved in that operation are principals in the new effort.)

“It’s not a vast right-wing conspiracy,” said Mr. Dillard, “but if you’re active on these issues, you build up networks of people who share your concerns, who are very involved, and who have very significant followings. These aren’t just ‘likely voters’—these are very serious, die-hard activists. And they all have readers and supporters.”

Visitors to the new site, he said, will find themselves at a one-stop shop of anti-Rudy messaging, material and merchandise, including anti-Rudy bumper stickers, T-shirts and other assorted items. (They will be sold at cost to avoid any kind of potential profit—and the F.E.C. scrutiny that would undoubtedly bring.)