A top Democratic dark money group poured hundreds of thousands of dollars into an unsuccessful effort to oust Sen. Deb Fischer (D-NE), records show.

Sixteen Thirty Fund, which is registered under a section of the IRS code called 501(c)(4) that allows “social welfare” groups to avoid disclosing their donors, spent over $800,000 supporting groups allied with Dan Osborn, who ran as an independent in Nebraska, according to Federal Election Commission filings.