Hollywood is already 80 percent shut down since the writers went on strike on May 2. While some television shows and movies continued filming, the writers were surprisingly effective in shutting down shows in production. If the actors join them on the picket lines, productions will be closed completely, a reality that will have a significant effect on the local economies in Los Angeles and other filming locales like Atlanta and New York City. During the last writers’ strike 15 years ago, the Los Angeles economy lost an estimated $2.1 billion.

The effects of a dual strike would also soon be coming to your television, with network shows going into reruns and a likely proliferation of reality television. Also, actors would no longer be able to promote new films, a reality that already exists to a large degree because the writers’ strike forced the late-night shows to go dark.

Not since Ronald Reagan was the president of the Screen Actors Guild have the writers and actors been on strike at the same time. Back then, the actors were fighting over residuals paid for licensing films for television. Today, the actors want to ensure higher wages and better residuals in an entertainment landscape in which studios are struggling to turn a profit after investing billions of dollars in streaming. The actors are also concerned about how their likenesses could be used with the advent of artificial intelligence.

Guild members authorized the strike in early June, with 97.9 percent of members voting yes. Then on June 24, Fran Drescher, the president of SAG-AFTRA, and Duncan Crabtree-Ireland, the national executive director of the guild, informed its membership that they “remained optimistic” about the talks. They added that the negotiations with the Alliance of Motion Picture and Television Producers, the trade association negotiating for the studios, had been “extremely productive.”

A video prompted a group of more than 1,000 actors, including Ms. Drescher, to sign a letter that urged the union’s leadership to not settle for a lesser deal. “We are prepared to strike,” the letter said.

On June 30, the union announced that it had extended its contract until Wednesday while the sides continued to talk.

After the parties negotiated all weekend, it remained unclear whether they were any closer to a resolution. Should they fail to make an agreement by midnight Pacific time on Wednesday, some 160,000 SAG-AFTRA members will be poised to join the 11,000 writers already on the picket line.