Super Tuesday and why it is important to the US presidential election

After starting small, the US presidential campaign has exploded into a nationwide contest that on Tuesday could all but decide the Democratic and Republican nominating fights.

Twelve states from Alaska to Massachusetts will hold caucuses and primaries that day, awarding a big chunk of the delegates needed to secure the two major party nominations.

The balloting marks a fundamental shift, away from the close-quarters campaigning in states like Iowa and New Hampshire and the drive for momentum that came with winning or, for the second- and third-place finishers, beating expectations.

Republican Donald Trump and Democrat Hillary Clinton, who start out ahead after winning three of four opening contests, seem likely to expand their lead in the delegate count Tuesday, or Super Tuesday as it has come to be known. The question is whether their margins prove insurmountable.

Trump holds the lead in most of the Super Tuesday contests, and will aim to deliver a knockout blow to Ted Cruz in Texas – the firebrand senator’s home state. Mr Cruz and Marco Rubio will both hope for a strong performance that convinces voters they are the consensus anti-Trump candidate.

Clinton’s sole challenger, Bernie Sanders, will hope to secure a handful of victories and enough delegates to stay within striking distance of the poll favored Clinton.

Because so many delegates will be awarded on a single day, Super Tuesday is one of the last chances for the candidates to change the trajectory of the election. If such a surprise fails to materialise, Mrs Clinton and Mr Trump’s paths to their parties’ nominations may well be paved on Tuesday.