During election season, much is talked about the vast sums of money raised and spent by politicians running for office. But often times these amounts are dwarfed by money spent by special interests in support or opposition to ballot propositions - which are questions placed on the ballot through petition or legislative action.

Unlike candidates for office, ballot measures often face little to no restrictions on contribution limits or spending, including in California where statewide campaigns rank among the most expensive in the nation. And at a time when partisan gridlock and bureaucracy have made pass legislation more difficult than ever, ballot propositions have become a convenient avenue for special interests to fast-track bonds, tax increases, regulations, and reforms.

As a result, proposition campaigns have become a cash cow for campaign consultants in California who charge millions in retainers and commissions to run expensive statewide efforts. We pulled up campaign finance data for ballot measures in America since 2000 and found that when it comes to spending on propositions, the Golden State is the golden goose for political professionals.

Generating the most money spent on any group of ballot questions since 2000 were California propositions 94, 95, 96, and 97, which sought to expand the scope of tribal gaming rights for four different bands of Native American tribes throughout the state. In total, roughly $172 million was spent both in support and in opposition to the measures, which passed before the voters in 2008.

Proposition 79, which would have given discounts on certain prescription drugs to low-income California residents, came in second at the ballot box as well as on our list of most expensive ballot propositions, having been defeated - 39% to 69% - after nearly $163 million was spent on both sides.

In 2006, oil companies went to the mats to defeat Proposition 87 which would have funded a $4 billion dollar program to reduce petroleum consumption. The total cost of the campaigns in support and opposition topped $155 million, making it the third most expensive ballot measure.

2012 saw two record-breaking campaigns in Propositions 32 and 30 - the former which sought to make it illegal for unions to deduct money from workers' paychecks for political purposes, and the latter a temporary tax on high-income earners to fund education. These battles, which pitted unions and corporations against each other, accounted for nearly 300 million dollars in campaign spending combined.

And Proposition 8, the famed 2008 California constitutional amendment that defined marriage as an institution between one man and one woman, drew $106 million in spending on both sides before being approved by voters 52% to 47%.

What about on the federal level? Every election, hundreds of millions are spent to get politicians elected, or to shut them down. Can you guess which politicians have had the most money spent to oppose them?

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