From: king@cogsci.ucsd.EDU (Jonathan King)
Newsgroups: alt.politics.elections
Subject: Estimating the Nth party vote (was Re: McPoll 10/8)
Summary: We're talking a maximum "definite" 2% here...
Date: 9 Oct 92 06:13:20 GMT
Organization: University of California, San Diego

jmk@cbnews.cb.att.com (joseph.m.knapp) writes:
>Latest daily tracking poll from USA Today/CNN:
>
>	Clinton 47,  Bush 35,   Perot 10
>
>The numbers have been more or less constant over the past week.
>The interesting part was how weak Perot's support is:
>
>                                   Clinton      Bush         Perot
>would definitely vote for:            33          22            2
>would definitely not vote for:        26          48           70

Thanks, once again for the polling data.  Looking at this, it occurred
to me you could use these data to figure out the maximum definite
support there could possibly be for other, less-publicized candidates.

First off, I'm assuming that the definite-for/not-for question was asked
of everybody polled; all bets are off if this isn't so.

Assuming this, if we additionally assume that people stating they were
definitely voting *for* a candidate would also state unequivocally
that they were *not* voting for that candidate's opponents, and if the
polled definite Libertarians (say) do the same thing, then some
candidate's "residual" definite-not totals provide one least upper
limit for the firm support any one Nth party candidate currently
enjoys.

Here's how it works: Take Clinton's definite-not total of .26, and
subtract Bush's definite-for total of .22 and Perot's definite-for
total of .02.  The remaining total of .02 is the proportion of those
polled who can't stand Clinton, but who are either undecided (or at
least uncommitted) on whom to vote for or who have decided to vote for
one of the Nth party candidates.  Thus, this proportion can be
construed as the sum of five terms, as follows, where

Residual Clinton definite-not = Bush-Perot-undecided + Bush-Nth-undecided
+ Perot-Nth-undecided + Bush-Perot-Nth-undecided + Nth-definite-for

Thus, Clinton's small residual definite-not proportion of .02 is thus
the *maximum* proportion of those polled who fall into any *one* of
these groups, so that it appears that definite-for Libertarian support
is AT MOST 2% right now, and probably somewhat even less.

But before all you Marrou and Fulani supporters out there get too
depressed, we should consider other possibilities:

* you people might be less likely to cooperate with the McPaper folk 
  doing the poll, 

* the non-inclusion of nth party candidates could skew the results some

* all the numbers going into this estimate are subject to (possibly 
  substantial) errors.  

In regards to the last point, however, if the poll's confidence
intervals are to be believed, then we can redo the calculation and see
what the maximum effect of the errors can be.  As it turns out, this
could *just* conceivably raise the Residual Clinton definite-not
proportion to .06, once again divided among the Nth party candidates
and the other (uncommitted but possibly leaning) groups.

In any case, the definite Nth party share doesn't appear to be very large,
at least as estimated from these data.

Comments?

jking