SEIU, American Crossroads look back at 2010 spending

POLITICO.com:
"Forti said he wasn’t sure whether GPS’s donors would have contributed had they faced the prospect of having their identities publicly revealed. “I don’t know if those people who gave to GPS would have given to the 527 or not. That’s impossible to know,” he said. “But they were more comfortable giving to a (c)4, so we created one.”

American Crossroads, which initially struggled to raise money, is incorporated under section 527 of the tax code, enabling it to accept unlimited contributions, but requiring it to publically disclosure its donors’ identities.

Meanwhile, section 501(c)4 of the code, under which Crossroads GPS is incorporated, allows groups to shield their donors’ identities, but requires them to spend a majority of their cash on apolitical purposes – an obligation Democratic critics say Crossroads GPS and other right-leaning groups flaunted during the campaign, when they bombarded Democratic candidates with bitingly critical ads.

“Disclosure was very important to us, which is why the 527 was created,” Forti said. “But some donors didn’t want to be disclosed and, therefore, a (c)4 was created,” Forti explained, referring to Crossroads GPS."