new coinage?

[Laurence Horn]

At 2:14 PM -0800 2/24/05, Jonathan Lighter wrote:
>I thought it was "tow" till I was in graduate school.  On the Erie
>Canal, a "tow-lines" were hawsers aboard a canalboat which, hitched
>to one of a pair of mules (on the "tow-path") would enable them to
>tow the boat for some distance.
>
>So it's not an eggcorn, dammit.  "Tow the mark" is an eggcorn !
>
>JL

But the way "tow the line" is used has nothing (obvious) to do with
tow-lines, and everything to do with staying under control, following
the rules, etc., the way a runner or diver does.  The OED has (under
_toe_ (v.)):
=======
To touch or reach with the toes; chiefly in to toe a or the line,
mark, scratch, crack, trig, to stand with the tips of one's toes
exactly touching a line; to stand in a row; hence fig. to present
oneself in readiness for a race, contest, or undertaking; also, to
conform, esp. to the defined standard or platform of a party.
=======
How do we get from using tow-lines to towing a boat to this meaning
of conforming to regulations?  (Not impossible, I grant, but less
obvious than toeing the line.)

Larry