Progressive activist Kyle Kulinski said Wednesday that 2020 presidential candidate Sen. Bernie Sanders Bernie SandersThe Hill's Campaign Report: Trump faces backlash after not committing to peaceful transition of power Bernie Sanders: 'This is an election between Donald Trump and democracy' The Hill's 12:30 Report: Trump stokes fears over November election outcome MORE (I-Vt.) is actually "at his best" when he shows off his famous grumpy side.

“Bernie — in my opinion — he's at his best when he’s an angry, old man because we all relate to that,” Kulinski, a co-founder of progressive political action committee Justice Democrats, told Hill.TV.

“People are mad, people are angry,” he added, citing the growing student debt crisis and current state of health care system. “We want somebody to reflect that — to reflect the dire situation that we’re in, and he by far, in a way, is most like that.”

Asked in an interview earlier this month to name a common misconception about himself, the Vermont senator joked that "there are some times" when he's actually not grumpy.

"They think I’m grumpy all of the time, and I’m only grumpy most of the time," Sanders said with a grin.

Sanders, who ranks among the top five White House contenders in most national polls, is one of the most progressive candidates seeking the Democratic presidential nomination.

In June, Sanders introduced a plan to cancel $1.6 trillion in outstanding student debt.

The legislation, which is being co-sponsored by Democratic Reps. Illhan Omar (Minn.) and Pramila Jayapal Pramila JayapalHillicon Valley: Subpoenas for Facebook, Google and Twitter on the cards | Wray rebuffs mail-in voting conspiracies | Reps. raise mass surveillance concerns Bipartisan representatives demand answers on expired surveillance programs DHS opens probe into allegations at Georgia ICE facility MORE (Wash.), also calls for public universities, community colleges and trade schools to become tuition-free. His main progressive rival, Sen. Elizabeth Warren Elizabeth WarrenHillicon Valley: Subpoenas for Facebook, Google and Twitter on the cards | Wray rebuffs mail-in voting conspiracies | Reps. raise mass surveillance concerns On The Money: Anxious Democrats push for vote on COVID-19 aid | Pelosi, Mnuchin ready to restart talks | Weekly jobless claims increase | Senate treads close to shutdown deadline Democratic senators ask inspector general to investigate IRS use of location tracking service MORE (D-Mass.), previously introduced a similar plan.

He has also long championed “Medicare for All,” a government-run system that would effectively eliminate private health insurance.

Sanders’s support for Medicare for All has become a subject of much debate within the Democratic Party.

Former Vice President Joe Biden Joe BidenPelosi slams Trump executive order on pre-existing conditions: It 'isn't worth the paper it's signed on' Hillicon Valley: Subpoenas for Facebook, Google and Twitter on the cards | Wray rebuffs mail-in voting conspiracies | Reps. raise mass surveillance concerns Fox News poll: Biden ahead of Trump in Nevada, Pennsylvania and Ohio MORE, who is running on protecting ObamaCare, has expressed concerns about the plan, saying it could result in a lapse in coverage for millions of Americans and possibly leave those with serious health conditions in limbo. Sanders hit back, saying these claims were "preposterous," sparking a heated back-and-forth.

Kulinski's comments come as Democratic candidates prepare for next week's second round of debates.

The two-night debate will air on CNN on July 30 and July 31. Sanders and Warren will be two of the biggest names to appear on the stage on the first night, while rivals Biden and Sen. Kamala Harris Kamala HarrisHundreds of lawyers from nation's oldest African American sorority join effort to fight voter suppression Biden picks up endorsement from progressive climate group 350 Action 3 reasons why Biden is misreading the politics of court packing MORE (D-Calif.) will be appearing the following night.

—Tess Bonn