Sen. Bernie Sanders has riled up Republicans and divided 2020 Democrats by pushing for the enfranchisement of all prisoners in the US.

Though only two states allow prisoners to vote — Maine and Vermont — it's quite common in countries across the world.

Canada, Israel, and South Africa are among over a dozen countries that allow prisoners to vote in all elections.

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Sen. Bernie Sanders has faced pushback from many Republicans and caused division among 2020 Democrats for saying all prisoners in the US — no matter how "terrible" their crimes — should be allowed to vote while serving their sentence.

But many other countries, including key US allies, already enfranchise current inmates on some level.

Canada, Israel, and South Africa are among over a dozen countries that allow prisoners to vote in elections.

There are 26 European nations that partially enfranchise currently incarcerated people, while 18 countries grant prisoners voting rights regardless of offense, according to a May 2018 report from People's Policy Project.

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In Germany, Norway, and Portugal, for example, the vast majority of prisoners are allowed to vote but those convicted of crimes that specifically target the "integrity of the state" or "constitutionally protected democratic order" are disenfranchised. Meanwhile, Iceland bans voting for those who've been sentenced to at least four years in prison.

The European Court of Human Rights in 2005 declared that blanket bans on prisoners voting violate human rights laws, which after a lengthy court battle led the UK in late 2017 to change its laws to enfranchise a small number of prisoners.

Sanders has responded to his critics on this issue by referencing the fact many countries around the world enfranchise voters.

"More than 30 countries around the world today such as Canada, South Africa and Finland allow prisoners to vote," Sanders said in a tweet on Wednesday. "This is not a radical idea. Every American citizen must be able to vote. Period."

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Allowing prisoners to vote is also the status quo in two US states — Vermont and Maine — and the US territory of Puerto Rico. Meanwhile, there are movements in states like New Jersey for lawmakers to enfranchise prisoners.

At present, roughly 4.5 million people in the US are affected by felony disenfranchisement laws. The number was closer to six million not long ago, but the passage of Amendment 4 in Florida last November helped change that by restoring voting rights to 1.4 million people with felony records.

There are roughly 7,100 people locked up in various ways in Vermont and Maine, meaning far fewer than 10,000 prisoners across the 50 states have the right to vote. In total, there are roughly 2.3 million people behind bars in the US.