BEIJING -- This Tuesday is a key date in US presidential election, when Democrats and Republicans in 12 states will choose their presidential candidates. Following is information about "Super Tuesday" and likely outcome of the primaries on the day.

"SUPER TUESDAY"

The US presidential election is divided into two parts: primary elections, where representatives of the Republican Party and the Democratic Party choose their presidential candidates, and the national election, where the entire nation votes to choose from the designated candidates.

In primary elections, party representatives of each state vote separately. Since 1988, many states decided to hold their primary voting on the same Tuesday sometime early in the year.

The day is often a deciding point in the primaries, producing a clear favorite to clinch party nomination, thus earning the name "Super Tuesday."

The number of states and the states participating in Super Tuesday vary each election season. The biggest Super Tuesday took place in 2008, when 24 states and US Samoa Islands held their primary voting on the same day.

This year's Super Tuesday encompasses 12 states: Alabama, Alaska, Arkansas, Colorado, Georgia, Massachusetts, Minnesota, Oklahoma, Tennessee, Texas, Vermont and Virginia.

Ten states will vote for both parties while Alaska will only hold Republican caucuses and Colorado only Democratic caucuses.

Altogether the Democratic Party will allocate 865 representative votes while the Republican Party will allocate 595 votes.

A Republican candidate needs 1,237 out of 2,472 total votes to bag party nomination, while a Democrat candidate needs 2,382 votes out of 4,763.

Among the voting states, Texas, Georgia and Minnesota are considered the most important ones as they have the highest number of representatives.

LIKELY OUTCOME

Republican candidate Donald Trump and Democrat candidate Hillary Clinton are projected to come out as winners of this year's Super Tuesday, as each have won in three out four states that have held primaries and are also enjoying a lead in the polls in the states that will vote.

However, both still face strong contenders within their own party that can pose a challenge to their presidential bids.

On the Democrat side, Bernie Sanders won the support of the young population, who helped him win in New Hampshire.

Sanders is less influential among the black and hispanic communities, making him weaker than Clinton in the Southern states, especially Texas.

Trump must face Ted Cruz and Marco Rubio, who are both Latino-Americans that were supported by mainstream Republicans.

Cruz won in Iowa and is expected to lead in Texas, a state he represents in Congress. Rubio trails in third.

Other candidates, such as John Kasich and Ben Carson may decide to drop the race if their results are disappointing.