[Butch7999]

mid50s, you seem to be conflating the OP's posts with our responses. The "what-ifs" are in the OP's original scenario.
He's since conceded that the runner is on 3rd only because of an error.
We were the ones who said defensive positioning is not a factor, and was not to be taken into consideration,
in determining whether the run was earned or unearned -- that was a key part of the OP's question.

Assumptions as to whether or not a runner would have advanced are not fuzzy supposition, they are the obligation
of the official scorer, and any assumption must be made in the pitcher's favor. In this scenario, the runner is safe at 2nd
perhaps/probably because of the error (we agree with you that there's insufficient detail in the way the play was described),
but definitively safe at 3rd only because of the error. Even if the runner is adjudged to have reached 2nd safely
without the error, it seems clear that the scorer cannot assume he would score from 2nd on a one-out single
(not two outs, if we're reading the original post correctly).
And of course, if in the scorer's judgment "ordinary effort" should have put out the runner attempting to steal,
then the question is moot, because in reconstructing the inning without the errors, there's no longer any baserunner at all.

Please consult MLB rule 9.16. "In determining earned runs, the official scorer shall reconstruct the inning without the errors...
giving the benefit of the doubt always to the pitcher in determining which bases would have been reached by runners
had there been errorless play."
That doesn't seem merely "quasi-accurate."
9.16
(c) No run shall be earned when scored by a runner whose presence on the bases is prolonged by an error, if such runner
would have been put out by errorless play.
(d) No run shall be earned when the scoring runner’s advance has been aided by an error... if in the official scorer’s judgment
the run would not have scored without the aid of such misplay.
(f ) Whenever a fielding error occurs, the pitcher shall be given the benefit of the doubt in determining to which bases
any runners would have advanced had the fielding of the defensive team been errorless.

Again, a convincing argument would persuade us we're wrong, but it'd be nice to hear a verdict from one or more
of the fellows on board who do in fact work as official scorers...

Wish we'd had a more interesting topic for post #400...