In the weeks since the Senate passed the Marketplace Fairness Act, which would let states force online retailers to collect sales tax, the behind-the-scenes action has been heating up. 

OpenSecrets reported on Monday that, following the 69-to-27 vote in May, a number of large companies have donated to members of Congress through their PACs. For example, Home Depot's PAC, which gave just $77,500 in donations during last year's presidential election cycle, donated $296,500 to campaigns and leaderships in June alone.

PACs for Target, Best Buy, JC Penney, Walmart, Lowe's, and Amazon have made contributions of up to $5,000 to Bob Goodlatte (R-Va.), who chairs the House Judiciary Committee and has promised to hold the hearing on the legislation and its effects. Rep. Spender Bachus (R-Ala.), chairman of the House Judiciary Committee on Regulatory Reform, Commercial and Antitrust Law, has seen contributions rise as well. 

Not all big corporations are in support of the bill, however. In fact, eBay CEO John Donahoe was one of the first to speak against the Marketplace Fairness Act, writing on April 21 to his company's customers about pushing for higher exemption limits. 

"The solution is simple: if Congress passes online sales tax legislation, we believe small businesses with less than 50 employees or less than $10 million in annual out-of-state sales should be exempt," he wrote. 

According to the latest filings, in the month of June, eBay's PAC donated $54,000 to members of Congress. The most notable donations were to members who attended a June 18 press conference for opponents of the bill, with $2,500 going to Rep. Steve Daines (R-Mont.), $1,500 to Sen. Ted Cruz (R-Texas), and $1,000 to Rep. Ron Desantis (R- Fla.).