Yet the gaps are growing smaller by gender and race, and bigger by income and education. A man born in 1950, who is now in the lowest 10 percent of household earnings, can expect to live 14 fewer years than a man in the top 10 percent, according to a Brookings Institution study. Smoking, the largest preventable cause of death, is more prevalent among lower-income and less-well-educated people, and accounted for a third to a fifth of the gap in life expectancy between men with college degrees and men with high school diplomas, according to Andrew Fenelon of the Centers for Disease Control and Prevention and Jessica Ho of Duke University.

Poor health makes it harder to work. Mr. Krueger found that 11.5 percent of men who were not employed cited illness and disability as a factor. Mr. Eberstadt’s analysis found that nearly two-thirds of American households where men were not in the labor force reported receiving money from at least one disability program in 2013.

American men are also far more likely than women to be in jail or to be convicted of a felony, compounding the difficulty of finding work. The government keeps almost no data on the 20 million men who are not in prison but have felony convictions. Mr. Eberstadt estimates that for men with a criminal record between 45 and 54, the odds of being out of the work force are 35 percent for white males and 40 percent for black males.

A segment of American men feel under cultural as well as economic assault.

Andrew J. Cherlin, a sociologist at Johns Hopkins University and the author of “Labor’s Love Lost: Rise and Fall of the Working Class Family in America,” directly links economic upheaval to the loss of masculinity. “It’s much more difficult now to say, I’m a real man,” he said. “A real man earns enough so his wife doesn’t have to work.”

Most economists, though, don’t believe it’s possible to go back to the days when manufacturing was king — and few women would want to give up economic or societal power, either. So what could help American men?

Many of the policies aimed at spurring economic growth and supporting low-wage workers would assist American men without college educations in particular.

In the short term, liberal economists and even some conservative ones back an idea that Mrs. Clinton has said she would push in her first 100 days — a $275 billion infrastructure jobs plan, which could provide at least temporary employment to a key segment of those hurting the most: blue-collar men.