5 Storylines to Watch Ahead of Last Major Round of Primaries

— -- On the second to last official primary day in the 2016 election, there's still a contest going on for one of the major parties, with voters in six states headed to the polls.

Here are some of the most compelling storylines to watch.

1. Clinton Clinches — Just Barely

Hillary Clinton has exactly enough delegates to win the Democratic nomination, according to ABC News estimates based on additional superdelegates tallied by the Associated Press Monday night.

Her total includes hundreds of superdelegates, who are not bound to a candidate, but even losses in California and elsewhere for Clinton today, while not anticipated, would not change that outcome.

This leaves Clinton the presumptive Democratic nominee for president and makes her poised to become the first woman in American history to secure a major-party presidential nomination.

Coincidentally, today is the eighth anniversary of the day that Clinton got out of the presidential race against Barack Obama, with her famous speech about cracks in the glass ceiling, after it became clear that Obama had a sizable majority of pledged delegates.

Even with enough delegates, she is still not the party's nominee; he or she is chosen next month in Philadelphia.

2. What's Next for Sanders

Sen. Bernie Sanders is under no obligation to drop out after Tuesday — or, for that matter, after June 14, when the last round of primary voting takes place, in the District of Columbia.

He is free to make his case to superdelegates, who are not obligated to formally commit to a candidate until the convention in Philadelphia, July 25 to 28.

Sanders has criticized the use of superdelegates regularly during his campaign speeches, but delegate math makes it clear that it’s impossible for him to secure a majority of delegates without using some superdelegates of his own.

Barring a blowout tomorrow by Clinton, she and Sanders will need the support of superdelegates to secure a majority at the convention.

3. Serious Ad Spending in California

Sanders has put down $2 million on television advertising in California, outspending Clinton but falling short of his outlays in previous important states, according to an ABC analysis of data from CMAG/Kantar Media.

Clinton, by comparison, spent $1.4 million on television ads in the Golden State.

Over the course of the campaign, the Sanders camp has regularly outspent Clinton on TV ads. For example, in New York he spent $5.7 million on TV ads, compared with Clinton's $3.9 million, and in Wisconsin he spent $2.7 million to her $1.3 million.

The latest Federal Election Commission reports show Sanders’ bank account has been dwindling. At the end of April, he was down to just $5.8 million after unloading almost $38 million during that month. He had more than $17 million in the bank at the beginning of the month.

4. Trump Leans on His Surrogates

While California has the most delegates up for grabs today, delegate-rich New Jersey is also heading to the polls.

And for Donald Trump, his endorsement by the state's governor, Chris Christie, may come in handy.

Trump was in New Jersey in May, helping host a rally turned fundraiser where attendees' $200 tickets helped pay down Christie's campaign debt.

"There is nothing like New Jersey," Trump proclaimed, before mentioning the state's "wiseguys."

5. Turning to the General Election

For months, Clinton and Trump have been sparring with each other as if they were already directly competing, but that matchup won't be official until the Republicans select their nominee at their convention in Cleveland, July 18 to 21.

A superPAC supporting Trump released a negative ad squarely aimed at Clinton, and her campaign unleashed its own attack on the presumptive Republican nominee.

The latest national survey by Quinnipiac University putting Clinton against Trump had her ahead, 45 percent to 41 percent, which was within the poll's margin of error.