Independent political groups have spent more than $2.1 million on Colorado’s Senate District 3 race, making the contest the state’s most expensive Senate campaign this election cycle, according to the latest campaign finance reports. The district, centered on Pueblo, is often described as Colorado’s last politically competitive Senate district. Its mix of Democratic representation at the state Capitol and support for Republican presidential candidate Donald Trump has made the race a closely watched test of the state’s political balance. Its result could help shape control of the Legislature and decisions on major policy issues next year. Republican Dana Charles is facing Democrat Aaron Gutierrez. The Senate Majority Fund, which supports Republican candidates, has spent $980,000 backing Charles. All Together Colorado, which supports Democrats, has spent $858,000 in the race, including about $723,000 opposing Charles and roughly $134,000 supporting Gutierrez. Coloradans for Accountable Government has spent another $537,000 in the past month. That spending includes $100,000 to support Charles and Republican Jonathan Post, who is challenging Democratic state Rep. Tisha Mauro in House District 46. The candidates’ own fundraising has been much closer. Through Sept. 30, Gutierrez had raised more than $126,000, including a small loan, compared with Charles’ $120,000. With about a month remaining before Election Day, Charles had nearly $61,000 available, about $9,000 more than Gutierrez’s $52,000. The outside groups’ spending is part of a wider push in three Senate races, where total campaign spending is approaching $5 million. Independent expenditure committees are legally barred from coordinating their activities with candidates. The Senate Majority Fund reported receiving $2.4 million in 2026 from a related political organization. GOPAC, which trains Republican candidates, contributed $1.04 million in September. GOPAC’s funders include business and industry groups such as the Colorado Hospitals Action Fund, the Colorado Bankers Association, Chevron and the Pharmaceutical Research and Manufacturers of America, as well as Altria and the Republican State Leadership Committee. All Together Colorado has raised $1.5 million since June 1. Its largest reported contribution was $200,000 from the Washington-based Sixteen Thirty Fund. Other contributors include AFSCME, the Colorado Education Association and Google. The other heavily targeted contests are Senate District 30 in Douglas County and Senate District 15, which includes Loveland and Berthoud. In District 30, the Senate Majority Fund has spent $923,000 to support Republican Sen. John Carson, who faces Democrat Kevin Leung. Leung had raised $181,955 through Sept. 30, while Carson had raised $166,514; both candidates had also lent money to their campaigns. In District 15, the Senate Majority Fund has spent $831,000 backing former Republican Sen. Rob Woodward against Democratic incumbent Sen. Janice Marchman. All Together Colorado had spent about $79,000 supporting Marchman. Through the end of September, Marchman had raised $229,000 to Woodward’s $168,000.