In a reprise of the Medicare wars triggered by last year’s budget debates, senior citizen and civil rights advocates today announced a grass-roots lobbying and ad campaign assailing House Budget Chairman Paul Ryan’s proposed budget.

“Domestic priorities will have to be drastically slashed” under the Ryan plan, said Nancy Zirkin, executive vice president of the Leadership Conference on Civil and Human Rights, at a “prebuttal” rally outside of the American Enterprise Institute, where the Wisconsin Republican presented his budget plan this morning.

Waving black and yellow signs that read “Hands Off My Medicare” and “Hands Off My Medicaid,” organizers at the event pledged to revive the town hall meetings that followed Ryan’s release last year of a budget plan that would have partially privatized Medicare.

The proposal Ryan released today takes a similar tack, replacing the program’s current model of government fees for services with a voucher-style system built on private insurance. Amid ongoing Congressional disputes over how to balance the budget, Ryan’s plan faces an uncertain future but has galvanized Democrats and their allies, who have set out to portray it as an assault on the popular entitlement program.

“When something is working, when something is efficient, when something is effective, we shouldn’t mess with it,” said Sister Simone Campbell, executive director of NETWORK, a progressive Catholic advocacy group, at today’s rally. Her group and other members of an interfaith coalition will release their own alternative “faith” budget on Thursday, Campbell said.

Also at the rally were organizers for Americans United for Change, who released a web video today that lampoons the Ryan budget as the sequel to a movie, dubbed “Young Guns II,” and promises: “If you like local TV stories about angry seniors chasing Republicans down the street, you’re going to love ‘Young Guns II.’”

Also in the works are Twitter ads promoting the video and additional TV and web ads in Congressional districts around the country, said a spokeswoman for Americans United. Other rally participants were the Alliance for Retired Americans, which announced plans to mobilize its members locally, and the Center for Economic and Policy Research, which is analyzing the economics of the plan.

Inside the AEI following the rally, Ryan said his plan will harness “choice and competition” to bring down the cost of Medicare, which he called “the debt driver of our economy.” His message: “What we propose actually brings Medicare into solvency.”