What's at Stake in Tuesday's Primaries

— -- Five states -- Connecticut, Delaware, Pennsylvania, Maryland and Rhode Island -- hold primaries today, which means big delegate hauls for both the Democrats and Republicans. See below for what's at stake.

Democrats

States voting: Connecticut, Delaware, Pennsylvania, Rhode Island, Maryland

Total delegates in states voting today: 464

Pledged delegates in states voting today: 384

Breakdown

As usual, the Democrats’ delegate allocation for pledged delegates is proportional, with a threshold of 15 percent. It is likely that both Clinton and Sanders will hit that threshold, as they have for the majority of the contests. But Hillary Clinton already has a head start on the superdelegates, uncommitted elected leaders and party officials who can vote for the candidate of their choice.

Of the 80 available in these states, Clinton has the support of 67, according to ABC News data. But despite this lead and her pledged delegate lead (she currently leads Sanders by 275 pledged delegates), Clinton will not have enough delegates to clinch the nomination tonight, even if she wins 100 percent of the pledged delegates.

But because this is the largest block of states voting until June 7, she will want to rack up as many pledged delegates as possible to increase her chances of clinching as soon as possible.

Sanders needs to win big tonight. If he wins 90 percent of the pledged delegates in all contests today, he can overtake Clinton's lead in that category. But given Clinton's substantial lead in superdelegates, she would still have a commanding delegate lead.

Republicans

States voting: Connecticut, Delaware, Pennsylvania, Rhode Island, Maryland

Delegates available: 172

Pledged delegates: 118

Breakdown

Polls show Donald Trump’s holding commanding leads in Connecticut, Pennsylvania and Maryland. Ted Cruz acknowledged Monday that tonight will be a good night for Trump. But his objective, along with Kasich, is to stop the front-runner from sweeping all 118 pledged delegates. The only state that is completely winner-take-all is Delaware, with 16 delegates.

If Trump wins Pennsylvania, the biggest prize, he will get all 17 at-large delegates, but there are 54 that are still unbound -- prime wooing opportunities for Kasich and Cruz.

In addition to persuading those Pennsylvania unbound delegates to support their campaigns, the most likely place to snag delegates from Trump is in Rhode Island, where candidates need to hit 10 percent of the statewide vote to get at least one. In Connecticut, they need to aim for 20 percent of the statewide vote, and/or win a congressional district to amass delegates.

In Maryland, the winner of the statewide vote gets all at-large delegates, and each congressional district is awarded on a winner-take-all basis. Given this allocation, Kasich and Cruz's best bet is to pick up delegates in a congressional district.