Last year, Wisconsin Governor Scott Walker set his sights on getting Illinois businesses to move to Wisconsin, and one of the few corporations to take him up on the offer received millions in grants and tax credits. That largesse might have translated into big contributions to Walker's campaign.

Buses paid for by the Koch-funded Americans for Prosperity (AFP), as part of its "Better Wisconsin" tour, and the Tea Party Express, with its "Reclaiming America" bus tour, converged in Madison, Wisconsin, Friday evening.

Both groups, which do not disclose who is bankrolling their operations, are touring Wisconsin on the eve of the election to rally voters to back controversial Wisconsin Governor Scott Walker and his allies facing recall. AFP, a non-profit under the tax code and not a registered PAC, has claimed its bus tour has nothing to do with the pending recall election; the Center for Media and Democracy has asked AFP to reveal who is funding its campaign, and the director of its state operations has refused. The Tea Party Express has also previously indicated that as a non-profit group under section 501(c)(4) of the tax code it need not disclose its funders.

Most of the headlines in recent weeks have focused on embattled Wisconsin Governor Scott Walker's effort to ward off a recall, but four Wisconsin State Senate seats are also up for grabs in the June 5 recall elections. These four elections could swing control of the Senate to the Democrats. Last summer, six senators faced recall elections, and Democrats picked up two seats. If they pick up one more seat in the June 5 election, they win control of the Senate and put a halt to the Walker agenda.