Sen. Dianne Feinstein, D-Calif., and a group of Capitol Hill lawmakers joined law enforcement officials, mayors, clergy and victims of gun violence Thursday to offer a new ban on assault weapons and high-capacity magazines like the ones used in recent mass shootings in Connecticut and Colorado.

But one thing was missing from the event, and necessary for the proposal to have any chance of passage: Republicans. None of the 14 Senate co-sponsors on the bill are Republicans.

Nor are any Republicans expected to attend a Friday roundtable discussion on gun violence in Richmond, Va., led by Vice President Joe Biden, who spearheaded the White House effort to develop a gun control plan.

Two Virginia Democrats, Sen. Tim Kaine and Rep. Bobby Scott, will participate in the discussion in the state capital, home to Republican House Majority Leader Eric Cantor. Biden’s office said Cantor declined an invitation to attend.

Republicans control the House of Representatives and hold 45 seats in the Senate, meaning that no gun legislation can get through Congress without some GOP support. And that assumes that all Democrats fall in line first, which also is not likely, given the highly charged politics surrounding the issue.

Despite supporters’ impassioned pleas to act, banning assault weapons and high-capacity ammunition clips face major obstacles.