While both John McCain and Barack Obama have endorsed a national cap-and-trade system as the centerpiece of their climate policies, the two proposals differ on several highly important grounds. The most important by far is the mechanism of permit allocation. Under the McCain system, permits to emit carbon would be granted for free to those with existing records of emissions; under the Obama system, all those wishing to emit will be required to buy permits at auction. The practical differences between the approaches are massive. Under the auction system, those who wish to pollute are made to pay. Under the free allocation system, those who have polluted in the past are granted valuable credits that they can either use to pollute or sell for cash.
As described before, consumers experience price rises in either scenario. What differs is where the windfall accrues. Under an auctioning system, it ends up in the hands of government, which can use it to fund low-carbon investments or refund it to the population as a hole (as in a cap-and-dividend system). Under a free allocation system, it simply goes into the coffers of the biggest polluters.
Even with a Democratically-controlled Congress and Senate, getting a plan based on 100% auctioning approved would be very challenging. Democrats from areas where extractive industries and automobile manufacture are economically important and politically powerful will resist policies that will be costly to dirty industries. That being said, it is arguably wiser to start with a policy position that is stronger than can probably be enacted and then compromise, rather than starting with a position that is weaker than necessary to get the job done.