A nugget in this must-read WaPo report, Battle for the Senate: How the GOP woke up while Democrats were feeling the drag:

Despite his deep aversion to super PACs, Obama in early 2012 reluctantly sanctioned Priorities USA, a super PAC set up to back his reelection, and allowed White House and campaign officials to appear at the group’s fundraisers. But Reid and Senate Democrats thought the president was not giving the same level of support for Senate Majority PAC.

Lawyers negotiated for months over legal minutia, with Obama’s counselors insisting that the president appear only as a guest and do no donor solicitation, which would have violated federal law. After Obama appeared at two Senate Majority PAC events — June 17 in New York and July 22 in Seattle — the president’s lawyers demanded that no staffer follow up with the donors for at least seven days.

These contingencies were so strict, Krone argued, that it would be fruitless to involve the president at all. “They were setting the rules as they saw fit,” he said. “For some reason, they hid behind a lot of legal issues.”

The White House maintains that it was prudent in protecting the presidency and avoid any appearances of a quid pro quo. The senior White House official voiced displeasure with Senate Majority PAC’s methods: “They were calling Obama donors who we had long relationships with and making asks that annoyed the donors.”