Provide a subtle "Read More..." or "Show All" button immediately after the truncated text (pick your favorite/most appropriate wording).
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Also, align the links/buttons that toggle this feature so that expanding then collapsing doesn't require moving the mouse. This would allow the user to "peek" briefly at the full content without requiring much effort.
Placing the expand/collapse function on the right would provide adequate separation from your radio button, so your users would be less likely to accidentally make a selection when trying to toggle the collapse.
If it seems appropriate or useful for your use case, consider adding an "expand all/collapse all" function as well. If there are many of these and your user would like to read everything, this could really help them out.