As he presided last month over his first field hearing in his home district, newly elected Rep. James Lankford (R-Okla.) praised the viewpoints of the business owners testifying before him.

“The best ideas come from individuals who see and breathe the issues not just from Washington,” Lankford said at the hearing on transportation funding held in Oklahoma City, according to the online news service Tulsa Today. “We have plenty of highly skilled and capable officials and workers right here that know the best way forward.”

He might have been familiar with a few of them before — they were also his campaign donors.

Two of the three construction company executives testifying had given Lankford checks of $2,400 or more. The third executive worked for a company whose employees were a source of campaign cash. Also testifying: the leader of an advocacy group who had given $500 to Lankford.

The contributors’ presence at the hearing — first reported by the Capitol Hill newspaper Roll Call — does not violate congressional rules, but watchdogs say it raises the question of whether expert panels are assembled based on their donations.

Lankford spokesman William Allison said that the witnesses were selected based on guidance from local industry leaders. “These gentlemen are nationally recognized leaders in their fields and were called as witnesses solely because of their expertise,” Allison said.

James Duit, one of the contractors testifying, said he was asked to participate by Bobby Stem, the head of the Associated General Contractors of Oklahoma. Stem said that he selected the witnesses to get a mix of representation from different parts of the industry.

“The vast majority of our members are donors to these campaigns,” Stem said. “It would be kind of hard to find some of our members who aren’t donors to Lankford and others.”

The Oklahoma hearing is not the only example of donors being asked to testify before members of Congress.

Brian Burgett, the chief executive of the Kokosing Construction Co., testified last month at a House Transportation Committee field hearing in Columbus, Ohio. Burgett had donated thousands of dollars to each of the campaigns of three of the lawmakers at the hearing, Ohio Republicans Jean Schmidt, Steve Stivers and Bob Gibbs.

Catherine Gatewood, a spokeswoman for Gibbs, said, “The panel was a group of professionals in transportation from across Ohio. Mr. Burgett’s company, Kokosing, is a major employer in the region.” Burgett did not return a call requesting comment.

Early this month, Rep. Renee L. Ellmers (R-N.C.) invited furniture maker and campaign supporter Jerol Kivett to testify on the burden of new health laws on his business. Kivett’s wife, Telia, donated $2,000 to Ellmers’s campaign, and the couple hosted a swearing-in ceremony for Ellmers at Washington’s Hay-Adams hotel. Ellmers’ s office had no comment. The Kivetts did not respond to a message seeking comment.

Some of the lawmakers hearing testimony from campaign donors are House veterans. Rep. Darrell Issa (R-Calif.) recently opened a hearing of the oversight panel he chairs by offering “full disclosure” that one of the witnesses was a personal friend, Tom Nassif, president of the Western Growers Association. Issa said for the record that Nassif was a deacon at the church they both attend, but he did not say that Nassif had given $4,800 to his 2010 campaign and a total of $13,800 over the past two decades.

Issa spokesman Frederick Hill noted that agriculture is one of the largest industries in California and, therefore, Nassif was an important part of the hearing on “Regulatory Impediments to Job Creation.”

“Mr. Issa certainly thought that [Nassif’s] testimony was both important and relevant to the hearing taking place,” Hill said. Nassif did not respond to a message seeking comment.

Donors to Democrats have also been congressional witnesses. Arnold Mitchem, president of the Council for Opportunity in Education, is scheduled to testify Thursday at a hearing on higher education. He has recently donated to the campaigns of two Democratic lawmakers on the Education and Workforce Committee, Donald M. Payne (N.J.) and Robert C. “Bobby” Scott (Va.).

Cessna chief executive Jack Pelton gave testimony Wednesday before an Energy and Commerce Committee hearing on job growth from exports. Pelton has given $4,800 to the 2010 campaign of freshman Rep. Mike Pompeo (R-Kan.), who serves on that panel and represents Wichita, the home of Cessna.

“It’s obvious that Mr. Pelton and Cessna have unique knowledge of international markets and trade issues,” Pompeo spokeswoman Rachel Taylor said, “making him well-qualified to speak to the economic benefits of export growth at this hearing.”