Republican Rep. Cory Gardner will move to the Senate in January, replacing Democrat Mark Udall, despite being outspent.
Voters strongly supported Ballot Measure 2A, a three-year, .3 percent tax projected to provide $27.6 million for cultural and public safety projects.
"[E]ven with a handful of counties still reporting, there just aren't enough options to get us across the finish line," Beauprez said Wednesday afternoon.
Voters across the state decided several issues -- from marijuana in Manitou Springs to a tax for pre-schools in Denver.
The midterms marked a drubbing for Democrats. Republicans picked up at least seven Senate seats, wresting control of the chamber and setting up a divided government for at least the next two years.
Is Colorado purple, blue, or red? "Colorado Matters" explores what it means when voters back a Republican for senator and Democrat for governor.
Colorado voters rejected three of four statewide ballot measures on Election Day.
The national Democratic and Republican parties poured millions into the contest, one of the most expensive races in state history.