There are 70 delegates up for grabs for Republicans tonight: 36 in Nebraska and 34 in West Virginia.
The Nebraska race stands to be a windfall as the delegates are allotted on a winner-take-all basis. Nine of the West Virginia delegates are allotted based on the popular votes in the state's three congressional districts, with each district controlling three delegates. The remaining 25 at-large delegates are determined by delegate preference.
The Democrats will be fighting over a total of 37 delegates in West Virginia, 29 of whom are pledged and eight superdelegates who can vote anytime until the July convention.
Neither of the primary races will be fully firmed up because of the outcomes of tonight's primaries.
An ABC News analysis has Hillary Clinton leading the Democratic race with a total of 2,228 delegates to Sen. Bernie Sanders' 1,454 total delegates.
In order to win the nomination using all remaining delegates, Clinton would have to win 16 percent the rest of the way and Sanders would have to win 97 percent.
That gap shrinks slightly if limited to pledged delegates only, in which case Clinton would have to win 34 percent of the remaining delegates while Sanders would need 66 percent.
All told, Clinton is much closer to securing the nomination. She has won about 93.5 percent of the 2,383 delegates necessary for the nomination. Sanders has won about 61 percent of the 2,383 necessary.
Donald Trump has an undisputed clearer path to securing his party's nomination because all his competitors have dropped out of the race.
He needs 35 percent of the remaining delegates to secure the GOP nomination, but even if he has a big win tonight and, hypothetically, won all the delegates at stake, he would still have a ways to go until he gets the 1,237 required to secure the nomination.
The ABC News analysis indicates Trump now has 1,077 total delegates.