In 2025, campaigns supporting and opposing 30 statewide ballot measures in nine states received $183.15 million in contributions.

The ballot measure receiving the most contributions was California Proposition 50, which authorized the state to use a new congressional district map. Campaigns supporting and opposing Proposition 50 received $172.7 million in contributions, with $124.9 million to supporting PACs and $47.7 million to opposing PACs. 

Proposition 50 accounted for 94.3% of the total ballot measure contributions in 2025. This is the highest share of total ballot measure contributions in an election year that a statewide ballot measure has received since at least 2015. The last ballot measure to come close to this share was in 2021, when Maine Question 1 received 93% (about $99 million) of the $107.64 million total contributions for all statewide measures in 2015.

Top donors supporting California Prop 50 included the House Majority PAC ($16.5 million) and Fund for Policy Reform ($10.0 million). The top donors opposing the measure were Charles Munger, Jr. ($36.0 million) and the Congressional Leadership Fund ($5.0 million).

The previous odd-year election, 2023, featured 41 statewide measures on the ballot across eight states—the most state ballot measures in an odd-numbered year since 2007—and $189.82 million in contributions supporting and opposing ballot measure campaigns. This was $6.7 million more than in 2025. The measure with the most contributions in 2023 was Ohio Issue 1, which saw $89.9 million in contributions to campaigns supporting and opposing the amendment, $82.8 million less than California Proposition 50. While Issue 1 of 2023 accounted for 47.3% of contributions in 2023, California Proposition 50 accounted for 94.3% in 2025. 

Since 2015, California Prop 50 has been the most expensive ballot measure in an odd-numbered year. The second-most-expensive odd-year ballot measure since 2015 was Maine Question 1 in 2021, which raised $99.9 million in contributions.

Besides California Prop 50, the other two most expensive ballot measures in 2025 were Maine Question 1, with $2.8 million in contributions, and Washington SJR 8201, with $2.6 million in contributions. These were followed by Maine Question 2, with $1.2 million in total contributions, and the campaigns around Colorado Proposition LL and Proposition MM, with $1.01 million for each measure.

Ballot measures in 2025 appeared in California, Colorado, Louisiana, Maine, New York, Ohio, Texas, Washington, and Wisconsin. Maine and Washington had the most contributions in 2025, behind California, with one measure in Washington and two in Maine. Maine had a total of $4.08 million in contributions, and Washington with $2.6 million. Last odd-numbered year, the states with the greatest contributions were Ohio, Maine, and Colorado—Ohio with $126.7 million total, Maine with $48.4 million, and Colorado with $5.8 million.

Of the 30 statewide measures on the 2025 ballot, two in Maine were citizen initiatives, meaning they were placed on the ballot through a signature drive. The campaigns for both citizen initiatives raised $4.08 million in contributions. The remaining 28 measures were referred to the ballot by the state legislature. Of the 28 measures, 11 of them had at least one campaign supporting or opposing the measure that reported contributions.