New York - New York's primary matters for both parties for the first time in decades. For front-runners Hillary Clinton and Donald Trump, it's about dominant victories to stop their rivals in their tracks. For their challengers, it's about staying in the game and preventing the lead vote-getters from a clear path to the nomination.

Here's a look at what to watch:

A delegate-by-delegate scrap

Clinton and Trump both have big leads in the polls, but their challengers are looking to peel off some delegates throughout the state. Texas U.S. Sen. Ted Cruz hopes to block Trump from cracking 50 percent in congressional districts across the state, which would help him lock down all 95 New York GOP delegates at stake. Vermont U.S. Sen. Bernie Sanders wants to keep down Clinton's delegate haul as well, and he has spent the closing days with events in vote-rich Manhattan and Brooklyn for a swath of the 291 Democratic delegates in the offing. It's why operatives here say there's not one primary but 27 - one for each of the Empire State's 27 congressional districts.

Battling for nonwhite voters 

Clinton built a commanding lead in the Democratic delegate race by racking up a string of wins in states with diverse voting populations in the South and West. Polls show she still dominates with minority voters, but Sanders could score a symbolic victory by carrying one of New York's boroughs or winning minority voters in exit polls. It's one reason both have zeroed in on Brooklyn, home to nearly 1 million registered Democrats.

Upping the ante in Upstate New York

Trump seems to have a lock on New York City, but he's trying to fend off Cruz and Ohio Gov. John Kasich in conservative parts of upstate New York. The three candidates have crisscrossed from stops in Albany, Buffalo, Rochester and Rome in search of frustrated Republican voters. U.S. Rep. Chris Collins, a Trump supporter from outside of Buffalo, said the billionaire is hitting "all the high notes" in his part of the state. "I believe Donald Trump could win all 95 delegates, but let's say it's 85," he told MSNBC on Monday. "It's still huge." Clinton, meanwhile, is looking to appeal to the same working-class voters in the region that voted for her in her 2000 U.S. Senate campaign while Sanders has focused on the industrially depleted western part of the state.

The home court advantage

There's probably no primary fight that's more personal than this one. Sanders was raised in Brooklyn before moving to Vermont, Clinton built her political career here. Both claim New York as home territory, and both have aggressively promoted their Empire State roots. The Republican side is just as divisive. Trump is a Queens native with an iconic tower bearing his name in Midtown Manhattan, and few attacks seemed to get under his skin more than when Cruz assaulted his "New York values."

The next round

The terrain for the front-runners looks likely to remain friendly in the next round of votes. Voters head to the polls in Connecticut, Delaware, Maryland, Pennsylvania and Rhode Island on April 26, and polls show Trump and Clinton with leads in most of those states. But even commanding performances by both in those races won't end the nomination fight. Sanders has made clear in recent days his goal, short of the nomination, is a fight at the party's convention in Philadelphia over a $15 minimum wage and other campaign promises. And Trump has an increasingly precarious path to the 1,237 delegates he needs to clinch the nomination, which could set up a floor battle over who should get the GOP nod.