Sen. Bernie Sanders is the first 2020 Democratic presidential candidate who supports enfranchising people who are currently incarcerated.

Other Democratic candidates like Sens. Elizabeth Warren and Kamala Harris have said they support enfranchising people returning from incarceration, but have only said that prisoners voting should be part of the "conversation."

Following the comments, Republicans have painted Sanders's idea as "radical."

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2020 Democrats across the board are in support of giving people convicted of felonies the right to vote after leaving prison, but Sen. Bernie Sanders on Monday took the idea a step further and separated himself from the rest of the field.

The Vermont senator is the only candidate vying for the 2020 Democratic nomination who supports enfranchising people who are currently behind bars, regardless of their crimes.

Much like the issue of reparations for descendants of slaves, this topic has driven a wedge between 2020 Democrats.

It's estimated roughly 4.5 million people in the US have been affected by felony disenfranchisement laws. Laws vary from state to state on whether or not current or former inmates are allowed to vote. At present, Maine and Vermont are the only two states where currently incarcerated people are enfranchised.

During a CNN town hall on Monday, Sanders was asked if he'd even support voting rights for rapists or people like the Boston marathon bomber.

Read more: Bernie Sanders says even 'terrible people' in prison for crimes like the Boston Marathon bombing should be allowed to vote

"If somebody commits a serious crime, sexual assault, murder, they're going to be punished. They may be in jail 10 years, 20 years, 50 years, their whole life," Sanders said in response. "That's what happens when you commit a serious crime."

"But I think the right to vote is inherent to our democracy. Yes, even for terrible people, because once you start chipping away…you're running down a slippery slope," Sanders added. "I believe even if they are in jail, they're paying the price to society, that should not take away their inherent American right to participate in our democracy."

Read more: Bernie Sanders says his idea of democratic socialism isn't like the 'authoritarian communism' of the Soviet Union

Republicans quickly denounced the Vermont senator's comments on voting rights for felons.

"Just when you thought it couldn't get worse," GOP Sen. Lindsey Graham said in a tweet, echoing McDaniel.

"@BernieSanders supports allowing rapists, murderers, and terrorists – like the Boston bomber and Dylan Roof, the individual who massacred 9 church-goers in Charleston, to vote from prison," Graham added.

Amid the backlash against Sanders from the GOP, a number of 2020 Democratic candidates have addressed this issue, but none of them are willing to go as far as the Vermont senator. And some completely oppose what he's proposed.

Here's where they stand.