The facts say so.

I have heard these claims, thought them to be false, but had not yet bothered to research them. For a politician with no scruples, all they have to be is plausible. Accuracy is nice but not required.

From Democrats Need a New Jobs Message: Debunking claims about U.S. workers. by James Freeman. Now that I look closely, I see the debunking is actually from Are most people actually working two or three jobs? Not really by Aparna Mathur.
The argument being made in some quarters:

Despite the steady positive news in the monthly jobs report, a recent talking point, oft-repeated, is that too many people are holding two or three jobs in order to make ends meet. Rep. Tim Ryan brought this up during the recent Democratic debate arguing that “the economic system…now force(s) us to have two or three jobs just to get by.” In the earlier debate, Senator Kamala Harris suggested that the low unemployment rate is not cause for celebration since for many Americans, this still meant working “two or three jobs” in order to make ends meet. Similar sentiments were expressed by Rep. Alexandria Ocasio-Cortez (D-NY), who during a PBS interview said “Unemployment is low because everyone has two jobs. Unemployment is low because people are working 60, 70, 80 hours a week and can barely feed their family.”

Well, time for some facts.

The Bureau of Labor Statistics (BLS) measures the unemployed by counting the number of people who are jobless, available for work, and have actively looked for a job in the prior 4 weeks. This means those working a part-time or full-time job are not counted as unemployed. The same person holding multiple jobs does not bring down the unemployment rate any more than that person holding one part-time or one full-time job does.

More importantly, the phenomenon of multiple jobholding itself is not widespread. As the chart below shows, multiple jobholding has been associated with periods of both high and low unemployment. Over the period for which BLS collects data, multiple jobholding peaked between 1995 and 1996 (6.2 percent of the population), at which point the official unemployment rate (U-3) averaged 5.5 percent. Over the course of the Great Recession, 5.2 percent of the population held multiple jobs, during which the official unemployment rate jumped to 9.3 percent. Since then, the multiple jobholding rate has continually declined. As of 2017, it was 4.9 percent. Trends also appear uncorrelated with the U-6 rate, which captures involuntary part-time workers (workers who work part-time, but do so for economic reasons and would rather work full-time). Irrespective of the unemployment rate, the long-run multiple jobholding rate is declining.

[snip]

Furthermore, are people actually working “60, 70, 80” hours per week? The BLS defines full-time workers as those working at least 35 hours per week. Those working 60 or more hours are workers with two full time jobs, a full time and part time job, or two part-time jobs that are nearly full-time. Data show that, among workers with multiple jobs, the vast majority are managing either one full-time job and a secondary part-time job or two part-time jobs. Only a tiny fraction (4 percent) work two full-time jobs. If we extrapolate their average daily work hours to a full week, multiple jobholders work an average of 42.95 hours per five-day workweek, relative to 39.7 hours for single jobholders, though they are also more likely to work on the weekends.

So, no, the unemployment rate is not low because people are holding multiple jobs.

No, the rate of people holding multiple jobs is down since from 1995/6 (6.2% of workers) to 4.9% today. Which is also lower than during the Great Recession when it was 5.2%.

And no, people are not working 60-80 hours per week. Multi-job holders work about 8% more hours than single full-time job holders, i.e. 43 hours a week instead of 40.

Mathur actually deals with a lot of the definitional issue of what constitutes work and compensation, acknowledging that the jobs marketplace keeps evolving and our means of measuring employment need to adapt.

But on the fundamentals - Yeah, the economy is working pretty well for everyone. The facts say so.