technology from back to front

Does Clinton beat Obama?

Here’s the graph of polling error against probability of victory we saw before, updated for the latest polling data:


So if you assume that the polls will be out by 5% or less, then Obama’s chances of victory against McCain are over 60%, but they dip under 60% when you assume a larger polling error.

However, that accounts only for random error in the polls; we assume that each state’s final tally will differ from today’s polls by a normally distributed value which is totally independent in each state. In reality, there is likely to be a systematic, country-wide change in his standing against McCain between now and voting.

Suppose he gains one percentage point countrywide. We can simulate that by just adding 1% to his margin in each poll and re-running the test:


With 1% extra his chance of victory is now between 60% and 80%, depending on how big you think the random error is. Now let’s take off 1%:


and we see that if he loses 1% he has less than a 50% chance of winning the election. Finally let’s bracket that with estimates for +2% and -2%:


Here’s the same picture, going by Clinton’s poll results against McCain:


which shows that if we assume a 5% error in the polls (a rather low estimate) then Clinton can lose 2% of her popularity nationally and still be virtually guaranteed victory.

Here are the two superimposed:


We see that if we assume a 10% error in the polls, then Clinton can lose 2% of her national popularity and still be ahead of where Obama is now.

No-one is talking about Clinton’s apparent huge advantage over Obama in the Electoral College. Is there some systematic error in the polling? Are Rush Limbaugh fans claiming to be Clinton supporters, as per his encouragement, to throw the Democrats into confusion? Or should the few remaining uncommited supers be throwing themselves behind the losing nomination candidate in a desperate bid to keep the one who will guarantee them victory in November?

Paul Crowley
  1. ((I accidentally deleted a bunch of comments I didn’t mean to delete today, so I’m having to repost them manually:))

    vanort wrote:

    Wow, talk about loosing sight of the forest for the trees. If we vote for who we’re told will win, rather then who we want, then we’ll never get who we want.

  2. ((I accidentally deleted a bunch of comments I didn’t mean to delete today, so I’m having to repost them manually:))

    tonyg wrote:

    Unless the person you’re told will win is the person you want.

  3. ((I accidentally deleted a bunch of comments I didn’t mean to delete today, so I’m having to repost them manually:))

    Paul Crowley wrote:

    I’m not advocating a vote for Clinton here – actually I think I’d advocate the opposite simply on the grounds that party unity is more important at this point – I’m just trying to add some useful data that might inform the debate. However:

    If you vote for who is electable with no regard for what you want, then what you want is forgotten. If you vote for what you want with no regard for who is electable, you end up in the People’s Popular Front of Judea, you make no real impact (except perhaps splitting the vote if the voting system is poor), and so what you want also goes out the window. If you want to play a meaningful role in the voting process, you have to make a measured compromise on this one.


× 2 = fourteen

2000-14 LShift Ltd, 1st Floor, Hoxton Point, 6 Rufus Street, London, N1 6PE, UK+44 (0)20 7729 7060   Contact us