WASHINGTON (AP) — Winning a party’s presidential nomination is like the children’s board game Chutes and Ladders spiced up with momentum, math and money.

In the delegate game, it costs millions to win a nomination and the stakes are huge, but the strategy is the same: Get to the finish line aided by ladders that give you a shortcut to victory while avoiding slipping down slides that put victory farther out of reach.

The race for the Democratic nomination starts out like a sporting event and finishes more like an accountant’s ledger.

Here are the game’s basic instructions:

THE DELEGATES

The only way to win the nomination is to gather a majority of delegates to the party’s national convention this summer. For the Democrats, this year’s only true contested primary, there will be 3,979 pledged delegates voting on the first ballot. There are also 770 superdelegates, though new rules will probably keep them from voting on the first ballot. More on superdelegates later.

The Democratic National Committee says the magic number to win the nomination on the first ballot is 1991 delegates.

These delegates will be pledged to the candidates who win them in primaries or caucuses. There is no rule that requires these delegates to vote for their candidate. However, they sign a pledge to reflect the will of the voters, and the campaigns can approve or reject them, so their loyalty has never been an issue, at least in the past.

About two-thirds of the pledged delegates will be awarded based on election results in individual congressional districts. The rest will be awarded based on statewide results. Every state awards delegates proportionally. Democrats banned winner-take-all primaries years ago.

But there’s a complication.

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THE THRESHOLD

This is the biggest pitfall, especially for marginal candidates. At the same time, it boosts top-tier hopefuls.

Winning delegates isn’t simple math. For Democrats, delegates get awarded proportionally to the share of the vote. But the catch is the minimum threshold.

A candidate needs to receive at least 15% of the vote just to get a delegate, and there’s no rounding up. A candidate with 14.99% gets zero delegates.

The threshold applies on both the district and state levels.

The minimum threshold eliminates candidates who can’t win in November, according to the Brookings Institution’s Elaine Kamarck, a longtime member of the Democratic National Committee who wrote the book “Primary Politics.”

The threshold gives an extra boost to candidates who make the cut. Once the initial votes are tallied, all the votes for candidates who didn’t make the cut are removed, and the percentages are recalculated.

For example, if Candidate A wins 20 votes out of 100 cast, Candidate A gets 20% of the vote. However, if 30 votes went to candidates who didn’t meet the threshold, those 30 votes are removed, and now Candidate A has 29% of the remaining votes.

That’s enough math for now. Let’s turn to the calendar.

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TIMING

The race starts on the first Monday in February with the Iowa caucuses and then moves to the New Hampshire primary, the Nevada caucuses and the South Carolina primary. These are February’s early four.

February isn’t really about delegates. Those four states award less than 4% of the delegates to the convention but are crucial because this is when momentum matters more than math.

Those first four contests are “more of a campaign for publicity, looking like a winner,” said University of Arizona political scientist Barbara Norrander. “The dynamic changes with Super Tuesday.”

March 3 — Super Tuesday — is the monster date on the primary calendar with 34% of pledged delegates at stake in 14 states, American Samoa and a group of expats called Democrats Abroad. Nearly half of Super Tuesday delegates come from south of the Mason-Dixon line.

Michael Bloomberg is skipping the February contests, spending big and jumping right to Super Tuesday’s delegate bonanza. Rudy Giuliani tried a similar tactic, with less money, in the 2008 Republican primary. He failed, as have others.

“After Super Tuesday, the only thing that matters is delegates,” said Josh Darr, a Louisiana State University political scientist.

Then the votes come in a big crunch. Voters award an additional 1,100 delegates on March 10 and March 17. By the end of St. Patrick’s Day, more than 61% of the delegates will have been won.

By that time, a clear front-runner will have probably emerged, and it will be difficult for anyone else to catch up. Remember, Democrats award delegates proportionally, so a front-runner with a lead of 100 or 200 delegates would have to completely flop in the late primaries for anyone else to catch.

This is how Barack Obama held off Hillary Clinton in 2008. Clinton won some big states late in the primary calendar, but she gained only a handful of delegates because she had to split them with Obama.

At this stage of the process, the big question will be whether the front-runner is winning a majority of the delegates — enough to clinch the nomination and avoid a contested convention.

St. Patrick’s Day also is the first date in which President Donald Trump can accumulate enough delegates to clinch the Republican nomination.

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SUPERDELEGATES

One of the biggest changes this year is that superdelegates — senators, members of Congress, governors, party officials — are staying on the sidelines, at least at first. Bernie Sanders pushed through this change after losing the nomination to Clinton in 2016. Sanders and other advocates saw superdelegates as undemocratic, even though they never changed the outcome of the primaries.

“We haven’t really seen a nomination contest where the Democratic Party voters prefer one candidate, and the superdelegates tip it to someone else,” University of Denver political scientist Seth Masket said.

Under the new rules, superdelegates won’t be able to vote on the first ballot unless the leader has such a big lead in the delegate count that their votes cannot change the outcome.

However, if no candidate wins a majority of the delegates on the first ballot — something that hasn’t happened since the 1950s — the superdelegates would play a huge role in deciding the nominee.

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Catch up on the 2020 election campaign with AP experts on our weekly politics podcast, “Ground Game.”