Republicans are spending heavily to defend competitive Senate seats in the final stretch of the U.S. midterms, but their money is buying less reach than the Democrats', according to a CNN analysis published Wednesday.

Citing AdImpact data across nine races last month, CNN reported Republicans spent $233 million on broadcast television to the Democrats' $121 million, while receiving only about 40 per cent more gross rating points. Democrats paid roughly $201 per rating point, compared with about $274 for Republicans.

The analysis attributed the gap largely to strategy and timing: Republicans relied heavily on outside super PACs, which pay premium late rates, while Democratic campaigns used discounted candidate rates and reserved advertising time earlier in the cycle.

A Republican strategist quoted in the report acknowledged that a spending advantage on its own was not translating into equivalent impact on the ground, a dynamic both parties are watching as the remaining competitive races enter their final weeks.