Even this far out, national primary polls have some correlation with outcomes: a candidate near the top is a somewhat better bet to win the nomination than one near the bottom.

Judged as of 2015 against historical analyses of early national primary polling and nomination outcomes (e.g. FiveThirtyEight, academic studies of polls from the year before voting). True: candidates leading early national primary polls historically won the nomination more often than low-polling candidates, with a positive but modest correlation. Mostly true: the correlation exists but is somewhat stronger or weaker than 'somewhat'. Mixed: the evidence is inconsistent across cycles or parties. Mostly false: analyses show essentially no meaningful predictive value. False: early poll standing is unrelated to, or negatively related to, nomination outcomes.

Set before the research began.

1. E1 How Reliable Are the Early Presidential Polls? Pew Research Center · 14 February 2007

   “In seven open Republican contests since 1960, the early front-runners held on to win the party nod six times.1 By contrast, early Democratic poll leaders won four out of eight open contests between 1960 and 2004.”

2. E2 Does an early lead in the polls usually hold up? Pew Research Center · 4 March 1999

   “In six open Republican contests since 1960, the early front-runner has held on to win the party nod five times.(1) But in six open Democratic contests since 1960, the early leader has won the nomination just once.”

3. E3 History Shows January Front-runner Often Does Not Win Democratic Nomination Gallup · 6 January 2004

   “there is no clear relationship between the candidate leading in Gallup's national trial heat surveys among Democrats at the beginning of an election year and the eventual winner of the party's nomination.”

4. E4 Winning the Presidential Nomination: National Polls and State Primary Elections, 1936-1972 Public Opinion Quarterly (Oxford Academic) · 1 January 1976

   “National public opinion is found to play a major role, and state primaries a much lesser role, in winning the presidential nomination.”

Pew's analyses found that early poll front-runners went on to win 10 of 15 open nomination contests from 1960 to 2004 (6 of 7 Republican, 4 of 8 Democratic) [E1], and 6 of 12 in its earlier 1999 count [E2]. These records show early front-runners winning most open contests overall, which fits a positive but modest correlation. A 1976 academic study also found that national public opinion played a major role in winning nominations [E4]. However, Gallup found no clear relationship for Democratic January leaders [E3], so the signal is weaker and less consistent for one party, though the overall evidence still supports the modest claim.