The bottom connector of the passenger-side front end drop link popped off. Replaced it with a new one (both sides were replaced) but the new one failed (as shown in the photograph) after one hour at VIR on a track day (the pace was, for a track day, not particularly aggressive). Wondering what might be causing the repeated failure... any thoughts? Thanks.

 

Your car lowered and if so did you increase the length of the link?

 

Bought the car already set up for track... if lowered, it isn't by much, but will look into it. Thanks.

 

If you have had this failure before there is something seriously wrong. I've never broke an end link on my race car in years of use.
Also that appears to be an low cost aftermarket link.
Post some pics of it installed and look to see if it has hit something else in the suspension.

 

Long shot, but disconnect both end links and make sure the swaybar is free to rotate in the bushings.

 

My bet is on this.