Holly, it mattered in 1968 who was in the White House. But RFK was assassinated and McCarthy (the leading vote getting who won the most primaries) was passed over by the Convention for Hubert Humphrey. This demoralized the youth and anti-war voters, giving Nixon the election by a tiny margin.
It matter in 2000 when Bush was given the election by the Supreme Court.
And it will matter this year, if we allow any of the Republican candidates to win. The policy agenda couldn’t be more different this year: repeal the ACA, defund Planned Parenthood, roll back environmental and financial protections, cut taxes on the rich, waste more money on defense programs that will never work (like orbital missile defense systems), do nothing to address excessive use of force by the police, try to deport 11 million illegal aliens, ban Muslims from entering the country, etc. etc. etc.