Which party took the Independent Trust Fund and put it into the General Fund?

Before I begin, bear in mind that this is an incredibly contentious issue, and a political football for both major parties.

Workers pay into the Social Security Trust Fund through a separate tax structure, and the money collected is invested in financial markets. If the Trust Fund runs a surplus from these collections (combined with interest earned from investments), the extra money can be given to the General Fund of the Treasury, in exchange for federal government bonds. Therefore, money isn't "taken out" of the Independent Trust Fund, but loaned to the Treasury. At the end of 2010, Social Security had a $2.6 trillion dollar surplus, which given current policy, will continue to grow until the year 2022. After 2022, the fund will decline until it is exhausted in 2033.

The General Fund *cannot* be "raided" by the Treasury; the Treasury can only borrow money, which it has an obligation to pay back (plus interest). Since this borrowing happens all the time, and the borrowed money is used for a variety of purposes, one party or the other will often claim that money has been "stolen" from seniors. This actually means that the Treasury is paying for something the complaining party doesn't like. Since there's always something one party thinks shouldn't be funded, and Social Security is such a potent political issue, politicians will continue to claim that funds were stolen, even though this has never happened.