Now we're mid-race, and we remember that the competitors are not thoroughbreds; they are sloths. They are creeping around the mile-and-a-quarter track so slowly that we can analyze each footstep, see what's coming well in advance. There's something to be said for a primary system that allows for 14 different narratives between each contest, and there are some things to be said against it, too. But it's the system we've got, and the sloths' footsteps demand some analysis. And so here we go.

The critical metric for Tuesday night's primaries is, as always, pledged delegates. How many more votes will each candidate rack up in the five states that will vote (Connecticut, Delaware, Maryland, Pennsylvania and Rhode Island) and how much closer will it put them to their respective goals? We've got some polls and we've got our copies of the rule book, and so we can, with some precision (hopefully) tell you where the sloths' feet will land.

The Democrats

As usual, the Democrats will split the delegates coming out of tonight roughly proportionally. And, as usual, the question is the extent to which Bernie Sanders narrows the gap by which he trails Hillary Clinton among pledged delegates.

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The answer is that he likely won't. After Clinton's big win in New York last week, Sanders campaign manager Jeff Weaver insisted that the race in Pennsylvania would be closer than recent polls suggest, which, again, is possible. But the most recent polling average in the state with the most delegates at stake tonight has Clinton up by 16 points. If that were to hold, Sanders would have to make up more than 30 delegates elsewhere.

Which itself isn't likely. In the RealClearPolitics polling averages in four of the five states to vote, Clinton leads by between 3 and 24 points — the latter lead coming in the also-large state of Maryland. There are 284 delegates at stake in Pennsylvania and Maryland, where Clinton's leads are largest. There are 100 delegates at stake combined in the other three, where her lead is more narrow. (The only recent poll in Delaware is an automated poll from Gravis Marketing. It shows Clinton up.)

Clinton comes into the night with a lead of about 237, according to delegate guru Daniel Nichanian's numbers. At the end of the night, that lead will grow. If current polling margins hold, she could end the night with a close-to-300-pledged-delegate advantage. It will probably be somewhat lower than that — but it's the wrong direction for Sanders.

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There are only two big states left on the Democratic calendar: New Jersey and California. Sanders will make up some ground in the smaller contests between now and when those states vote in early June, but the delegate math continues to be prohibitive.

The Republicans

The Republican side is, as usual, messier.

The mark that we're watching is whether or not Donald Trump makes significant progress toward the 1,237 delegates he needs to clinch the nomination — a mark that keeps moving in and out of his grasp.

Tonight should help. The five contests on the Republican side all have five different sets of rules, but we can overlap those rules with recent polls (again, using RealClearPolitics averages and that Gravis survey in Delaware) to estimate totals.

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Connecticut: Trump has a big lead, topping 50 percent in the recent polling average. If that holds, he'll get all 13 statewide delegates, plus three delegates in each of the state's five congressional districts that he wins. The odds are good he'll win all five (especially if he wins the state with a flat majority), so that's 28 delegates for Trump.

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Delaware: Delaware is winner-take-all, and Trump appears to have a big lead. An easy calculation: Trump gets 16 delegates.

Maryland: Trump leads here, too. If he wins the state, he gets 14 delegates, and another three for each congressional district he wins. As in Connecticut, it's likely he'll win most of them, if not all. So let's say he gets 35 or 38 out of 38 delegates here.

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Pennsylvania: Pennsylvania, as we've noted, doesn't matter much in the pledged delegate count. Yes, it has a lot of delegates, but most of them aren't bound to the state's winner. So Trump will probably win, but he'll only get 17 delegates whom he can rely on for a vote at the convention. (Many running to be among the 54 delegates available in the states' 18 districts have said they'll vote for the winner of their respective districts, but we can't really put them down as pledged delegates.)

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Rhode Island: Rhode Island is the only proportionally allocated state on the docket for tonight. The 13 statewide delegates are given out according to how candidates perform overall. What we'll watch for here is if Ted Cruz breaks the 10 percent threshold for getting a slice of that pie; if he doesn't, he's shut out of delegates and Trump's total could increase. In the state's two congressional districts, the top three finishers over 10 percent get a delegate each, so that's a wash. So in Rhode Island, Trump will get around 10 delegates.

In total, then, Trump will pick up 106 or 109 delegates (unless he wins or loses more congressional districts in Maryland and Connecticut). That larger number would bring his total pledged delegates to 957 — 280 shy of what he needs to clinch. He, too, is running out of time. After tonight, there are only 502 more delegates to win, meaning that Trump would still need to win more than half. That's easier than it would be for Sanders, since he can win more delegates than he does percent of the vote. But it's not a sure thing.