Joe Biden v Donald Trump - where contest will be won and lost

The Republican primary race is not officially over but with no obvious pathway to victory for Nikki Haley, a general election showdown between two adversaries is coming into view.

We are months away from the Democratic and Republican conventions, the moment when each party officially unveils its presidential nominee.

But the 2024 election seems all but set in stone.

The contest between Joe Biden and Donald Trump will be unique in modern history as a rematch between the current president and his immediate predecessor.

"Having two presidents running changes the nature of the race," says Todd Belt, a politics professor at George Washington University.