Do consider the cost-per-vote numbers before donating.
In 2000 there were just over 100,000,000 votes cast while candidates spent $162,000,000 (
source)
Soft money got another $450,000,000 in 2000 (
source: common cause)
For a total of about $600,000,000 in 2000.
But you have to consider that 80% of those 100,000,000 votes were pretty much set in stone before the campaign began, so there were only 20,000,000 votes in play. And you could pretty much discard all but the swing states, so let's throw out half of them. So you're spending $600,000,000 and only pursuing 10,000,000 votes.
That's $60 per vote. And that's in 2000, and this one's gonna cost more than that. So I bet you could do much better by intelligently spending that money.