But what if the top issue hasn't arrived yet? 
Remember in '08 it was the recession, in '20 it was covid. We didn't see those coming early in the election process.
Not to dispute that those were the main issues of the general elections, but the primary happens much earlier in the year and most of the discourse around it is set more than a year before the election. The top issue in the 2008 Republican primary was not the recession, and in the 2020 Republican primary it was not COVID. Inasmuch as primaries have "top issues" -- a questionable suggestion -- the top issue in the 2008 Republican primary was still foreign policy and support for the War on Terror (see the fairly long-lasting lead for foreign-policy-emphasizing Rudy Giuliani and an eventual victory for McCain); Romney and Huckabee both ran on messages with more of the 2010s in them but were unsuccessful (though both did quite well). In the 2020 Republican primary the top issue for Weld's challenge of Trump was just Trump's personality, with maybe immigration as a secondary issue.
Since I've been paying attention to US politics -- so, since 2007 -- the narrative for a primary has usually been set in the summer before a general election year (summer 2007, summer 2011, summer 2015, summer 2019). Presumably the narrative for the 2024 primaries will be set in the summer of 2023.
This creates discontinuities, by the way: neither Obama nor McCain really wanted to run in a recession-focused election. Extremely lengthy campaigns create their own dynamics which change the
zeitgeist in odd ways: Romney was a better candidate for November 2011 than November 2012, and Hillary better for November 2015 than November 2016.
Global health ending up as the main issue of our first (...but certainly not last) campaign between two septuagenarian candidates feels, if anything, weirdly appropriate.
Poll
