Mr. Biden is right that only after the Obama administration left office did the extent of Russia’s effort to influence social media become clear. But the hacking into the Democratic National Committee — a crime — was clearly understood, and the Obama administration reaction — expelling 35 diplomats who were actually spies, and closing some Russian facilities inside the United States — is today considered too little, too late.

What the Facts are:

Mr. Sanders was asked how he could convince voters, at a time of low unemployment, that the economy would do better under a democratic socialist than under President Trump.

What Mr. Sanders said:

“The economy is doing really great for people like Mr. Bloomberg and other billionaires. In the last three years, last three years, billionaires in this country saw an $850 billion increase in their wealth. But you know what? For the ordinary American, things are not so good. Last year, real wage increases for the average worker were less than 1 percent. Half of our people are living paycheck to paycheck.”

The second claim is true. After adjusting for inflation, wages for production and nonsupervisory workers increased by 0.7 percent from January 2019 to January 2020, according to the Bureau of Labor Statistics.

The third claim is also true, according to several surveys of American families. In one such survey, the First National Bank of Omaha found 49 percent of Americans say they expect to live paycheck to paycheck this year.

The first claim is more difficult to assess. Calculations by the economists Emmanuel Saez and Gabriel Zucman of the University of California, Berkeley, who have estimated wealth shares across the income distribution in the United States and scored Mr. Sanders’s proposed wealth tax, suggest that the top 400 wealthiest Americans have collectively gained about $500 billion in wealth over the last three years. There are more than 400 billionaires in America, though — and there is a debate among economists over how to properly measure the wealth they hold.

What the facts are:

Mr. Bloomberg highlighted rising life expectancy in New York City, where he pursued an aggressive public health agenda.

What Mr. Bloomberg said:

“Before I left, life expectancy in New York City had grown by three years during our 12 years in office such that, when I left, it was three years greater than the national average.”

Mostly true. Mr. Bloomberg is correct that life expectancy in New York City is higher than it is in the United States overall and that it rose disproportionately during his tenure as mayor. New York is in many ways a model city in improving the health and longevity of its low-income residents. By the end of his tenure, life expectancy in the city had improved by three years, according to a city health department analysis, though the gap between the city’s and the nation’s life expectancy at the end of his time in office was a bit lower than he claimed, more like 2.3 years.