The last major primaries of the 2016 White House race kick off on Tuesday in New Jersey and California, hours after the United States delegate counts showed Hillary Clinton clinching the Democratic nomination.

The first polls opened at 6 am in New Jersey, with voting to begin four hours later in California, the country's most populous state. Passing the milestone of 2,383 delegates late on Monday secured Clinton's status as the presumptive Democratic nominee, and she becomes the first female standard-bearer of a major US political party.

It's a dramatic political resurgence for a highly experienced but controversial candidate who lost to Barack Obama in their 2008 battle for the Democratic nomination.