Having embraced Donald Trump for the presidency, the National Rifle Association is planning a major push to nationalize its “concealed carry” campaign, which has already enabled millions of citizens to go armed into public places in the name of self-defense.

Republican lawmakers, ever enthusiastic about the gun lobby’s agenda, will control both houses of Congress next year when Mr. Trump assumes the presidency. His campaign celebrated the N.R.A.’s fantasy that citizens can stand up to gunmen by shooting it out. Research refutes this idea; it is far more likely that guns are used to harm the owners or other innocent people than to stop a crime.

There were eight million Americans with concealed-carry permits in 2012, according to federal data. That number has been growing rapidly with the gun lobby’s success in loosening state restrictions, making it possible for permit holders to pack guns in university classes and many public venues. The N.R.A. goal in the Trump administration is to pass an expansive national law that would require states to recognize concealed-carry permits issued by other states. Varying Republican proposals in Congress range from focusing on a special permit applicable in all states to a broad mandate that would force states with tight restrictions to accept a visitor’s right to carry a weapon, even if that person came from a state with lax permit standards or no permit requirement at all.