Democratic presidential front-runner Joe Biden is taking heat online after a viral clip showed him putting his hands on an Iowa voter who asked about climate change, then instructing the voter to not support him.

"I'm going to support you if you win the nomination because we got to get rid of Trump but what are we going to do about climate change?" the man, identified as Ed Fallon, asked Biden.

"We have to stop building and replacing pipelines," Fallon added.

Biden responded by placing his hands on Fallon, pushing him away, then angrily telling Fallon to not vote for him.

"Go vote for someone else [if] you're not gonna vote for me in the primary," Biden responded.

Biden then chided Fallon for asking to take a picture with the former vice president, and reiterated that he did not want Fallon's support if Fallon did not plan to caucus for him.

Fallon later responded to the incident, which took place on Sunday, in a blog post where he criticized Biden as the Democratic candidate least likely to defeat President Donald Trump.

He wrote:

[D]espite his repeated calls for unity, Biden rejects my offer to support him in the general election. That really shocked me. What was even more shocking was how Biden pushed and poked me, and then took hold of my jacket with both hands as he lectured me.

I've said this before, and I'll say it one more time: Joe Biden is the Democratic candidate LEAST likely to beat Donald Trump. His demeanor on the stump will inevitably come back to bite him, perhaps repeatedly. His propensity to violate personal space is a huge non-asset in politics, and his frequent gaffes are prime fodder for opponents and the media.

Fallon, as he told Biden and explained in his blog post, is supporting billionaire Tom Steyer in the Iowa caucuses next month.

Steyer responded to the viral video Tuesday, accusing Biden of taking out his frustration on Fallon.

Fallon served in the Iowa General Assembly from 1993-2006. He also unsuccessfully ran for Congress and governor of Iowa.