Sen. Chris Murphy (D-Conn.) is a mainstream progressive known for supporting a tougher U.S. approach to Saudi Arabia and stricter gun safety regulations.

In December , though, he began taking up a cause not typically on Congress agenda: an epidemic of loneliness in the United States that Murphy believes is quietly at the heart of the bitterness and violence wracking the country.

Were all searching for the reasons why theres been a retreat to very hair-trigger hostility and violence in this country, Murphy told HuffPost in a phone interview in March. Were all trying to understand why Donald Trump did so well despite the fact that he focused all his energy on tax cuts for the very elite.

Ive come to the conclusion that theres a lot of things that unite Americans that we refuse to see, and one of those things is the way that many of us are increasingly feeling very lonely, very isolated and increasingly disconnected, he added.

In discussions in the press and with colleagues, Murphy makes the case that the rise of social media and the isolating effects of the COVID-19 pandemic have turbocharged the United States already-depleted communal infrastructure and norms. That has, in turn, helped fuel growing rates of mental illness, substance abuse, violence and even, some studies show, right-wing extremism .