Sanders gave 2016 Democratic nominee Hillary Clinton a run for her money during the primary. He won 23 states and had more than 13 million votes.
Kasich was the last Republican to drop out of the race against the GOP nominee Donald Trump. Kasich won his homestate of Ohio and had more that 4 million votes nationally, putting him in third behind Texas Sen. Ted Cruz.
The debate starts at 9 p.m. tonight and will be moderated by Dana Bash and Jake Tapper.
There will be a lot for the two former presidential candidates to talk about - the latest news on Trump, Russia and the FBI is sure to come up.
However issues such as jobs, trade and healthcare are also likely.
This isn't the first time Kasich and Sanders have had a public debate. In 1995 Sanders testified before the House Budget Committee, which Kasich chaired, about welfare reform.
During a primary stop, a Sanders impersonator showed up at a Kasich event and thanked him for keeping it classy.
It should be an interesting event. Follow along with us tonight on Twitter at @Ohio_Politics
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