The Center for Responsive Politics is taking a deep dive into the information available on political non-profits, highlighting the spending, connections and reporting by the groups.

Among the organizations they've highlighted: The Alliance for a Better Minnesota. The Alliance, which has registered nearly every flavor of political group allowing it flexibility in its fundraising and spending, popped up as a group that reported vastly different spending numbers to the Internal Revenue Service and the Federal Election Commission.

According to the Center, the Alliance reported $3.8 million in spending to the IRS in 2008 and told the IRS that year that it spent $754,000 on politics. That same year, it reported $1.4 million in spending to the FEC.

The suggestion from the Center was that the group was underreporting its spending.

Asked about the Center's numbers, Alliance executive director Carrie Lucking dismissed the notion that the numbers reported to the separate federal agencies should match.

Five years ago, she said, the reporting laws were different. The Alliances political spending through the nonprofit registered as a 527 group were reported to the FEC and other expenses from a 501 (c) 4, another type of non-profit, were reported to the IRS. The two types of political nonprofits operate under different reporting rules. For an explanation of how 527s differ from 501(c)4s click here.

"There is no discrepancy, there were different types of expenses reported to the appropriate enforcing agency," Lucking said in an email.

Asked about Lucking's explanation, the Center's editorial and communications director Viveca Novak said that it is valid to compare the two numbers.

But she also said that in the wake of the question, the Center added language to its report noting that "IRS and FEC definitions of political spending are not identical" and they changed the headlines in two of their charts. The group also added that, "some experts say that organizations should not imagine there's a practical difference between what the two agencies are asking for."

Read more about the Center's work to disclose information about political non-profits at OpenSecrets.org.