BELOIT, Wis. -- A Wisconsin billionaire who is Gov. Scott Walker's largest campaign donor owed no state taxes in 2010 because of a change in her corporation's structure.

According to records from the state Department of Revenue and ABC Supply Inc., Diane Hendricks' tax obligation dropped from $2.2 million in 2009 to zero in 2010. Hendricks owns ABC Supply, the nation's largest wholesale distributor of roofing, windows and siding. Hendricks had a seven-figure tax bill in four of the previous five years, the records show.

Hendricks, a financial supporter of conservative causes, and has given Walker's campaign more than $500,000. She recently garnered attention when a documentary trailer was released that showed her and Walker discussing Republican strategies. The video captured Walker talking about a "divide and conquer" strategy in dealing with state employee unions in his budget adjustment bill. The legislation curtained collective bargaining for most public employee unions and touched off huge demonstrations that will culminate in a recall election next week.

"Now ABC is paying taxes on its own," Bianchini said.

Despite the 2010 bill, Bianchini said ABC and Hendricks have paid their fair share in taxes.

"Diane Hendricks and Ken Hendricks paid $10 million in taxes since 2005," Bianchini said, adding that focusing on the tax bill of zero in 2010 is "meaningless and minutiae."

As a national company, Hendricks and ABC Supply have paid millions of dollars in taxes in other states, he added.

Forbes Magazine estimated Hendricks' March net worth at $2.8 billion. Hendricks and her husband, Kenneth, built ABC Supply. She became chairman of the company after her husband died in 2007. The company posts annual revenue of more than $4 billion.

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Here is a preview to "As Goes Janesville," where Hendricks and Walker appear.