Iowa caucuses: Race to decide election candidates begins

The first event that will help decide the candidates for US president is to take place with Monday's Iowa caucuses.

Democratic and Republican voters will choose their preferred nominees for the White House race.

While victory in Iowa doesn't guarantee anyone the nomination, it can help give them crucial momentum.

The path appears clear for Donald Trump to be the Republican nominee, but there are still 11 people running for the Democratic nomination.

Many have spent the past few weeks vigorously campaigning in the Midwest state, which is always the first to vote. The primaries contest goes on until early June, and moves on to New Hampshire next Tuesday.

Here's the story of what to expect in Iowa, broken down.

Polls suggest that Bernie Sanders has risen to be the favourite in Iowa (or - depending where you look - the joint-favourite, with former vice-president Joe Biden).

He is one of four senators running for president who have had to stay behind in Washington to attend Mr Trump's impeachment trial, but his supporters, including Alexandria Ocasio-Cortez, a well-known congresswoman, have been energetically campaigning on his behalf in Iowa.

Four years after losing out to Hillary Clinton, could this be the 78-year-old's time? He is backed by a huge pot of donations and a team of hundreds. But if he won the nomination, would moderate Democrats really rally around a candidate for the White House who identifies as a democratic socialist?