If either of Rep. Martha McSally's Republican primary challengers had won, Democrats would have a better chance of picking up the Arizona Senate seat. | Chip Somodevilla/Getty Images Mystery super PAC that attacked McSally was funded by Senate Democrats

A mysterious super PAC that spent $1.7 million attacking Republican Rep. Martha McSally during the Arizona Senate primary was funded entirely by Senate Majority PAC, a super PAC aligned with Senate Democrats, new campaign finance disclosures show.

Red and Gold spent money solely attacking McSally in the days leading up to the August Arizona primary, where McSally — the favored candidate to win — was battling two other candidates, Kelli Ward and Sheriff Joe Arpaio.


If Ward or Arpaio had won, it would have given Democratic candidate Kyrsten Sinema a better shot at winning the open seat come November, which gave Democrats an incentive to attack McSally in the race.

The new disclosure shows that Senate Majority PAC, the main super PAC aligned with Senate Democrats, seeded Red and Gold with $1.7 million as it started attacking McSally in early August. Red and Gold ran attack ads that said McSally supported an “age tax” that led older people to pay significantly more for health insurance.

“It’s an age tax, plain and simple,” a woman said in one Red and Gold ad. “Martha McSally puts Washington ahead of Arizona.”

Morning Score newsletter Your guide to the permanent campaign — weekday mornings, in your inbox. Email Sign Up By signing up you agree to receive email newsletters or alerts from POLITICO. You can unsubscribe at any time. This site is protected by reCAPTCHA and the Google Privacy Policy and Terms of Service apply.

The attacks did not do enough damage to keep McSally out of the general election: she won the primary with more than 50 percent of the vote.

Super PACs are by law supposed to disclose their donors before primary elections. But Red and Gold used an increasingly common loophole of changing its filing schedule with the Federal Election Commission — switching from quarterly to monthly filing deadlines at a strategic moment — which allowed it to avoid having to file disclosures on certain dates before the primary.

Because of the loophole, Red and Gold first spent money in the Arizona primary on August 4, more than two weeks before the August 28 election, but filed its first disclosure on September 20, three weeks after the election was over.

After McSally won the primary, several other prominent Democrats contributed money to Red and Gold: Billionaire megadonor George Soros gave Red and Gold $600,000, Renaissance Technologies Founder James Simons gave it $500,000 and AWM Investment Company President Austin Marxe gave it $100,000.