With 384 Democratic delegates at stake, Tuesday's primaries offer Sanders one of his last, best chances to gain ground on Clinton — but pre-primary polls didn't offer him much hope. [...] watch his evening speech in Huntington, West Virginia, for any hints of resignation. Trump needs a big delegate haul Tuesday to preserve his slim hopes of locking up the GOP nomination during the primaries. The candidate who likes to compare himself to a champion boxer eager to quickly end the fight has little margin for error. Look for Trump, who'll speak from Trump Tower on Tuesday night, to dangle the Cruz-Kasich alliance as evidence of a corrupt political system and a sign of his own strength. The fact that his two rivals needed to join forces against him, Trump says, "shows how pathetic they are." The state awards Tuesday's biggest chunk of Republican delegates, but it won't be a quick and easy matter to determine who gets them. [...] the other 54 — three from each of 18 congressional districts — are directly elected by voters and don't have to commit to a specific candidate. The prospective delegates' names will be listed on the ballot with no information about which presidential candidates they support. Exit polls will offer new clues about whether primary voters are ready to coalesce around their parties' leading candidates come November.