For example, 77 percent of the 5.8 million employed in personal care and service occupations are women; 72 percent of the 17.7 million people working in office and administrative support occupations are women; and 75.6 percent of the 8.9 million in health care occupations.

Democratic operatives and union organizers are starting to mobilize lower-paid service workers in preparation for the 2018 midterms and the 2020 presidential elections. The Service Workers International Union is gearing up for a major political and union organizing campaign in the Midwest.

The SEIU is the nation’s second-largest union and one of the most politically active. It has been a driving force in the minimum wage “Fight For $15.” The union has organized such low-wage employees as janitors, protective service workers, home-care workers and airport workers. It is trying to put itself into a position where it can register and turn out workers in such areas as fast food employees, warehouse and fulfillment center workers and hospitals.

Union officials estimate that there are 64 million workers across the country who make less than $15 an hour.

“Only half are registered, and only half of them voted. 48 million of them did not vote in 2016,” one union leader, who asked not to be identified so that he could be forthright, told me. A big problem last year, he said, was that

Hillary Clinton didn’t inspire anyone. Why the hell stand in line if it’s just to vote for more of the same?

Stan Greenberg, a Democratic pollster and strategist, wrote me by email to say that he thinks Florida’s analysis “is very smart.” Greenberg, like many pollsters, had been broadly categorizing voters without college degrees as working class, but recently he has begun to change the practice:

For the first time, we are asking occupation to try to get at this — and so, I think there really is potential for Democrats to gain here. This is a real insight into what is possible.

Paul Booth, who recently retired as executive assistant to Lee Saunders, president of the American Federation of State, County and Municipal Employees, noted that service workers have been crucial to the survival of the union movement. For decades, trade unions have provided crucial money and manpower to the Democratic Party. In an email, Booth wrote me:

Service industries are where the growth strategies of organized labor have been mostly focused for 40 years, and where most of the growth has occurred. While union membership has stagnated on the bottom line at around 16 million over that span, the composition of the 16 million changed dramatically, millions of health care, personal service, education and government workers (and some retail) joining, while roughly the same number in other sectors “leaving.”

Republican leaders, Booth argues, are fully aware of the dangers of an organized and politically mobilized service sector. “The effort to strangle this opportunity has been the top strategic priority of the GOP” since it gained power in the 2010 midterm elections, he contended. These efforts include state right-to-work legislation, ending automatic deduction of union dues, severe restrictions on the issues permitted at the bargaining table, and other restraints on organized labor.

Booth notes that in 2014, Democrats and unions successfully backed ballot initiatives to raise the minimum wage in three red states, Alaska, Arkansas and South Dakota, “but little or none of the support spilled over to help Mark Pryor, Mark Begich and Rick Weiland,” the losing Democratic Senate candidates in those states.