This nice congruent conflation of “red line” and “line in the sand”, both meaning the furthest limit of what will be tolerated, was uttered by Kasie Hunt on MSNBC last week (Craig Melvin hosting). “Line” appears in both idioms, which is probably the root of the confusion. Ms. Hunt is probably too young to remember the song, “Red Sails in the Sunset”, so it probably does not enter the mix. A big thanks to Frank King for hearing this one and sending it in.
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