This means that Crossroads spent at least $85.7 million on political activities, not the $74.5 million the group reported to the IRS on its 2012 tax return. It also means political activities made up about 45 percent of Crossroads' total expenditures.
Here's how ProPublica did the math:
Americans for Tax Reform told the IRS in its tax return, obtained and made public by the watchdog group Citizens for Responsibility and Ethics in Washington (CREW), that it raised and spent about $31 million in 2012. Since the group got $26.4 million from Crossroads, only $4.6 million of its revenue came from other donors. At least $11.2 million of Crossroads money had to go toward the political ads reported to the FEC.
That means Americans for Tax Reform spent about 51 percent of its money on political ads reported to the FEC in 2012.
TPM has emailed a spokesperson for Crossroads and will update this post if he responds.