The US city where Republicans are due to hold their national convention in August declared face masks mandatory on Monday amid a new surge in coronavirus infections.
The party relocated its convention to nominate President Donald Trump for reelection to Jacksonville in Florida earlier this month, after Charlotte, North Carolina, mandated strict social distancing measures.
The new regulation came as infections soar in the southern state, forcing it to reinstitute partial shutdowns and other restrictions.
The state health department reported 5,266 new infections and 28 new deaths due to COVID-19 on Monday.
The state's totals rose to 146,341 confirmed cases and 3,447 deaths.
"At 5 p.m. today, the city of Jacksonville will be adopting a mandatory mask requirement for public and indoor locations, and in other situations where individuals cannot socially distance," the city government said in a statement.
"Please continue to practice personal responsibility to help stop the spread of this virus."
On June 11 Republicans announced they would move their nominating fest, which brings together thousands of party members in a normally closely packed hall, to Jacksonville, attacking the strict rules set for the Charlotte convention.
At the time Trump attacked North Carolina governor Roy Cooper, saying he "is still in shelter-in-place mode" and "doesn't want to give an inch."
North Carolina too has seen a recent rebound in COVID-19 cases, but not as severe as Florida's, which is home to a massive tourism industry.
People flock to popular Ocean Drive in Miami Beach, Florida on June 26, despite a surge in coronavirus infections in the state