There are lots of links between primaries and general elections. Is the counterpoint that underperformance in a primary (low turnout) is not significant in predicting performance in a general? If so, where are the studies that show a lack of significance? I just got the below from a quick google. And for the record, I don’t have an agenda LULZ, I’m just answering your question.
The 2016 election is a clear data point. Hillary had marginal turnout in the primary and underperformed in the general. GOP had relatively high turnout in the 2016 primary.
Midterm 2018 primary had solid Dem turnout and then made big gains in general.
https://www.nytimes.com/2018/03/06/upshot/texas-primary-democrats-voter-enthusiasm-turnout.html
In early voting, Democratic primary voters outnumbered Republicans in Texas by a margin of 52 percent to 48 percent. The number of Democratic early voters, presumably motivated in part by distaste for President Trump, more than doubled compared with 2014.
https://www.jstor.org/stable/pdf/2111323.pdf?seq=1
Using ordinary least-squares regression, we find that divisive presidential primaries do indeed have a deleterious effect on the general election results. Specifically, when one party has a divisive primary season while the other party's nominee is essentially uncontested, then the divided party will be adversely affected in November.