Does that adage stand up to scrutiny?
Let’s take a look.
Since 1972, when the modern-day presidential primary and caucus calendar started to take shape, 17 winners of the primary have gone on to capture either the Democratic or Republican nominations, with nine (including incumbent presidents) going on to win the White House. Just 7 winners did not go on to win the nomination in that time.
On the Democratic side, then-former Georgia Gov. Jimmy Carter captured the 1976 primary on his way to winning the nomination and eventually the presidency. Four years later, the incumbent president won what was a bitterly contested primary. Carter went on to grab the nomination over challenger Sen. Ted Kennedy of Massachusetts but lost the general election to former California Gov. Ronald Reagan.
Massachusetts Gov. Michael Dukakis won the 1988 primary on the way to winning the nomination, but he lost the general election to Vice President George H.W. Bush.
President Bill Clinton won a slightly contested 1996 primary before winning the nomination and re-election. Four years earlier a second-place finish was as good as a first – as then-Arkansas Gov. Clinton came in second to favorite son Sen. Paul Tsongas of neighboring Massachusetts. But Clinton’s surprise second-place finish earned him the nickname "comeback kid," propelling him to the nomination and the presidency.
Vice President Al Gore won the 2000 primary on the way to winning the nomination. He narrowly lost the general election to then-Texas Gov. George W. Bush that came down to a controversial decision by the Supreme Court.
Then-Sen. John Kerry of Massachusetts won the 2004 primary before winning the nomination but losing in the general election to Bush.
President Barack Obama won a slightly contested 2012 primary before winning the nomination and re-election.
On the Republican side, President Richard Nixon won a contested primary in 1972 before winning re-nomination and re-election to a second term in the White House.
In 1976, President Gerald Ford won a highly contested primary against Reagan on his way to capturing the nomination. He lost the general election to Carter.
Reagan won the primary in 1980 on his way to capturing the nomination and the presidency. Reagan easily won a slightly contested primary in 1984 before winning re-nomination and re-election.
Then-Vice President Bush won the 1988 primary ahead of taking the nomination and capturing the White House. Four years later, President Bush won a contested primary against Pat Buchanan ahead of capturing the nomination but losing the general election to Clinton.
In 2004, President George W. Bush easily won a slightly contested primary ahead of re-nomination and re-election.
Four years later, Sen. John McCain of Arizona won his second New Hampshire primary (he won in 2000 as well) before capturing the nomination but losing the general election to Obama.
Former Massachusetts Gov. Mitt Romney won the 2012 primary on his way to capturing the nomination before losing to Obama in the general election.
Four years ago, Donald Trump’s victory in the New Hampshire primary vaulted him toward the GOP nomination and eventually the White House.