Voters who don't for president

Is there data on how many people nationally and per state show up to the polls but decline to vote for any of the presidential candidates? Also looking for the same data for today’s election.

This has become an increasing concern since the 2000 election. Only a relatively small number of voters choose to vote but deliberately leave the presidential election blank. (My mother did it once, so I know the number isn’t zero.) High rates of presidential undervoting are an almost fail-safe indicator of problems with the voting apparatus.

This article has some useful information:

I can’t find any numbers for 2004. For 2008, you’ll have to wait until the Secretaries of State publish results in a month or so, and then start canvassing web sites.