right now OBama proposes that the capital gains tax rules as they stand right now do not change, except for the top 2% (people earning more than 250 thousand a year).
That means right now, if things remain the same, persons in tax brackets at 15% or less will not pay any capital gains tax on long term gains.
Obama's plan calls for allowing the current law to expire as schedule in 2010, and to extend it for those in the lower brackets so that they can continue to benefit from the already favorable 15% rate; and no tax for those in lower brackets. (hence, they would as quoted "pay not one penny more in taxes). Obama may change the eligible brackets for not paying capital gains to a higher bracket, say those in the 20% or lower brackets. it is really too soon to tell.
Keep in mind, that despite the campaign rhetoric to the contrary, the capital gains tax prior to Clinton was still favorable for the upper brackets. (its all smoke). The capital gains was, depending on the he year and type 22 to 28 percent versus being taxed as regular income at 35% for those upper brackets.
If McCain gets in, you can expect the current rates to remain the same and to be extended indefinitely.
Not sure if this is what you were looking for, please let me know.