Super Tuesday: What is it and why is it important? Published 25 minutes ago This video can not be played To play this video you need to enable JavaScript in your browser. On 5 March, voters in 15 states and one US territory choose candidates for president. It should offer a glimpse of Joe Biden and Donald Trump's strengths and potential weaknesses. The Republican contest will be in all of these 15 states, while the Democrats will vote in the same states except Alaska.