SALEM, Ore. (AP) — Democratic U.S. Sen. Jeff Merkley's campaign says a conservative super PAC is buying television ads, presumably to boost Merkley's Republican rival.

Merkley spokesman Andrew Zucker said Thursday that Freedom Partners Action Fund purchased nearly $1.5 million worth of airtime beginning Aug. 6.

Freedom Partners is an independent expenditure committee linked to the Koch brothers, who are major donors to conservative candidates and causes.

The outside money could help close a fundraising gap between the campaigns for Merkley and Republican Monica Wehby. It also shows that big donors haven't been scared off by reports that two former partners called police on Wehby as their relationships deteriorated.

Wehby's campaign said Thursday that she raised $950,000 during the second quarter — about half as much as Merkley.

Freedom Partners did not immediately respond to a request for comment.