New York: Polls opened Tuesday in the US state of New Jersey, on a day of decisive primaries in the race for the White House.
Voting began hours after US networks` tallies showed Hillary Clinton securing enough delegates to clinch the Democratic nomination and become the first female standard-bearer of a major US political party.
However, the former secretary of state has not yet claimed victory, urging supporters to vote and help push her to a strong finish.
Her campaign acknowledged "an important milestone" but Clinton said the Democratic race was not yet over.
"We are on the brink of a historic, historic, unprecedented moment," she told a rally in Long Beach, California on Monday.
"But we still have work to do, don`t we?" she said, referring to Tuesday`s primaries in California, Montana, New Jersey, New Mexico, North Dakota and South Dakota.
Clinton, 68, has survived an extraordinarily strong grassroots campaign by her party rival Bernie Sanders and is set to go head-to-head with Republican real estate tycoon Donald Trump in an unprecedented showdown for the White House.
But Sanders was not ready to capitulate, insisting the Democratic nominee will not be chosen until delegates vote at the party`s national convention in late July.
The Vermont senator has long argued the system is tilted against him, with hundreds of "super-delegates" aligning with Clinton before he even entered the race last year.
Sanders, looking for big victories Tuesday, contends he will use the coming weeks to try to flip many of Clinton`s super-delegates in his favor.
Nancy Worley, chair of Alabama`s Democratic Party, is one of the so-called super-delegates -- current and former elected officials and political activists who are not bound to vote for a specific candidate -- who in a last-minute flurry pushed Clinton over the threshold.
She explained how she had yet to commit to a candidate until Monday, when she received phone calls from three US news outlets.
"If the popular vote is overwhelming and the delegates are very much in her camp, in my opinion, it`s kind of crazy not to unify the party and move forward to defeat Donald Trump," Worley told AFP, noting how Democrats in her state chose Clinton by a wide margin.
Clinton has vowed to "do everything I can to unify the Democratic Party," saying she would reach out to Sanders.