Colorado could play a key role in picking a presidential nominee on Super Tuesday.

Hillary Clinton and Donald Trump could be significantly closer to a presidential nomination after Super Tuesday, or their challengers could make a stand.

Democrats will allocate 66 delegates to Clinton and Sanders, proportionally. Both candidates said it's an important state. The GOP will also caucus, but there won't be a statewide result.

Volunteers are working hard to get as many Colorado voters to caucus.

"Door knocking, phone calling, lit drop, door hangers. We've been staying up late already," said Dulce Saenz with the Bernie Sanders campaign.

In order to participate in the Colorado caucus, voters needed to register as a Democrat or Republican by Jan. 4. During the town hall meeting, people will physically pick a side for their candidate.

The one million unaffiliated voters in the state don't get to participate and if you're not able to make it to your caucus location by 7 p.m. Tuesday night, you're also out of luck.

The Bernie Sanders' and Hilary Clinton campaign offices are making a last minute push to explain how caucusing works and what it means for their candidate.

"It's work. You just don't walk in and vote for two minutes," said 9NEWS Political Analyst Floyd Ciruli.

Ciruli expects around 100,000 voters to show up to the contest that's big for Democrats but not for Republicans, who won't chose a statewide winner.

"The problem with that is that there's no excitement right now," he said.

Republicans will still caucus and discuss candidates but no statewide result will be declared. That way, delegates can wait before deciding whom to support at the national convention.

As for the Democrats, volunteers and politicians will try to sway as many undecided voters as they can to their side to stand and be counted on Tuesday.

"The caucus process is a conversation and people get to advocate for one side or another and what we will find tomorrow night is there will still be people going to their caucuses who are undecided," said Former U.S. Secretary of the Interior and Hilary Clinton supporter Ken Salazar.

Caucuses take around an hour or longer depending on your precinct's size.

Here are the Democratic caucus locations:

Here are the Republican caucus locations: