Daniel Gordon, the administrator of the Office of Federal Procurement Policy, avoided discussion of the order, saying it would be "inappropriate" for him to comment on what is only a draft and not official administration policy, though he did defend the principle of transparency.
"Transparency is one of the best ways of fighting corruption," Gordon said, calling it "Vitamin T."
That did not win over opponents of the proposal.
Rep. Sam Graves (R-Mo.), chairman of the House Small Business Committee, said small businesses would be "ill-prepared" to handle the draft order's disclosure requirements as well as its potential criminal liability. He added that asking for political contribution information from a company during a contract's bidding process disturbed him greatly.
"The simple idea that you want this information ahead of time disturbs me in a big way," Graves said.
While being careful not to discuss the draft order, Gordon said a contractor's politics would never come into consideration for a contracting officer when awarding a contract.
"They won't take that into account. The only factor that you take into account is the [contract solicitation]," Gordon said.
Republicans were not the only ones to question the draft order. Rep. Gerry Connolly (D-Va.) said while he favors transparency, people could draw "a false assumption" from data detailing government contractors' political contributions.
"By changing this process at this time, it could have a chilling effect on people who want to participate in the political process," Connolly said.
Other Democrats spoke forcefully in favor of the draft order.
Rep. Elijah Cummings (D-Md.), the Oversight Committee's ranking member, said in his 15 years as a member of the panel he had never seen the committee oppose more transparency. He also noted much of the information at stake is already disclosed at the Federal Election Commission.
"Following this logic, no disclosure is appropriate," Cummings said.
The draft order comes after outside groups, many that didn't disclose their donors, sponsored a flood of campaign advertising last election. That came after the Supreme Court's Citizens United decision last year, which freed up corporations and unions to spend unlimited funds on electioneering activities.
The White House and Democrats tried to pass the Disclose Act last year to counter that court decision. The legislation would have forced outside groups to disclose their donors, but it failed to pass Congress after stalling in the Senate.