Back in January FiveThirtyEight and the Cook Political Report mapped out the number of delegates that each of the presidential candidates needed to win for each primary/caucus in order to clinch their party's nomination by their respective national conventions this summer. Briefly, here's how they made their estimates (for more detailed information on their methods and assumptions, see "Who's on Track for the Nomination"):
For the GOP candidates, they relied on a three-step process. First, they utilized three variables — education, religious affiliation, and state and congressional district partisanship — to model the candidates' geographic support in primaries and caucuses. For example, they assumed that Donald Trump would perform best in states and districts with small shares of college graduates, while Ted Cruz would do better in places with large shares of evangelical protestants. Next, they translated this support into delegates based on the delegate allocation rules in each contest. Finally, they calculated individualized, state-by-state delegate targets for each candidate. For example, they estimated that to be “on pace” to win 1,237 delegates by the Republican convention, Cruz would need to win 47 of South Carolina’s 50 delegates, while Trump would need to win just 38.
Their estimates for the Democratic candidates followed a similar logic but drew on slightly different assumptions. In particular, they based their estimates on the racial composition of the Democratic electorate in each state, how each state lines up on a liberal-conservative scale, and whether Democratic voters live in rural or conservative areas. They assumed that Sanders would do better in whiter, more liberal, and more rural states, while Clinton would do better in states with more nonwhite voters.So why do I claim that Bernie Sanders is doing almost as well as Donald Trump? Because heading into the Wisconsin primary next Tuesday, Sanders has captured 92% of his delegate target up to this point (1,038 out of 1,129), while Trump has captured 95% (752 out of 789). The difference, of course, is that Trump holds a substantial lead over Ted Cruz and John Kasich, while Sanders lags behind Hillary Clinton. Trump has clearly benefitted from a campaign in which he was pitted against a large number of "establishment" Republican candidates, while Sanders has essentially had to go it alone against Clinton. In many respects, it's remarkable just how well Sanders has done.
All this suggests at least two things: First, Sanders could still has a shot at being the Democratic nominee (although it is a long shot) and, second, Trump may not secure enough delegates to clinch the GOP nomination before the convention (although he is in a good position to do so). In fact, if he doesn't, there's a very good chance someone else will walk away as the Republican nominee ("It’s Probably First Ballot Or Bust For Donald Trump At The GOP Convention").
Note: For FiveThirtyEight's and the Cook Political Report's state-by-state targets for each of the candidates, as well as how well each candidate is doing with respect to those targets, see "Who's on Track for the Nomination."