When ExxonMobil Chairman and CEO Rex Tillerson appears before the Senate Foreign Relations Committee Wednesday, all of the Republican senators and one of the Democrats considering his nomination as secretary of State will have something in common—they have received generous campaign contributions from ExxonMobil’s Political Action Committee since Tillerson took over as CEO.

According to campaign finance reports, the ExxonMobil PAC made multiple donations to all of the GOP senators on the committee, totaling between $11,000 and $23,000 each since 2006. The most money went to Sens. Cory Gardner (R-CO) and Johnny Isakson (R-GA), who each received $23,000 for their political campaigns. Sens. Marco Rubio (R-FL) and Rob Portman (R-OH) received $20,000 each over the same period. The PAC gave $17,000 to Sen. John Barrasso (R-WY), and $15,000 each to Committee Chairman Sen. Bob Corker (R-TN), Sens. Ron Johnson (R-WI), Rand Paul (R-KY), and Jim Risch (R-ID). Sen. Jeff Flake (R-AZ) received $11,5000, while newly-elected Sen. Todd Young’s (R-IN) campaign brought in $14,500. The lone Democrat on the committee to get a PAC contribution was Sen. Tom Udall of New Mexico, who received a one-time $2,500 donation in 2013.

The donations to members of the Foreign Relations Committee were among hundreds of contributions the PAC made to dozens of federal lawmakers over the course of Tillerson’s leadership. He himself gave the company’s PAC a total of $50,000 as CEO.

Above and beyond Tillerson’s contributions to the company’s PAC, he spread another roughly $500,000 in personal contributions to a network of Republican committees, parties, and individual candidates, including more than $170,000 to the National Republican Senatorial Committee, more than $90,000 to the Republican National Committee, and contributions to the campaigns of House Speaker Paul Ryan and Senate Majority Leader Mitch McConnell.

Long a familiar face in Republican circles, Tillerson was a surprise pick for Trump to become his nominee for secretary of State. Although he has no formal diplomatic or government experience, he has led ExxonMobil, the world’s largest publicly traded oil and gas company, as it expanded its complex operations into new regions around the globe.

When he appears before the Foreign Relations Committee Wednesday, he is expected to be grilled on his role leading the company as it did business overseas. In some cases, that business included working through a subsidiary to operate in Iran, Syria, and Sudan, three countries considered by the U.S. government to be state sponsors of terror. Tillerson will likely explain those and other actions that ExxonMobil took internationally with him at the helm.

While Tillerson’s and ExxonMobil’s financial support for senators who will vote on his nomination is significant, it not unique among the wealthy nominees who sometimes populate presidential administrations, including Trump’s. The Washington Post reported this week that Betsy DeVos, Trump’s Education secretary nominee, and her family members have donated more than $250,000 to five Republican members of the Committee on Senate Health, Education, Labor and Pensions, which will review her nomination later this month.

But Sen. Bob Menendez, a senior Democrat on the Foreign Relations Committee who has not received donations from ExxonMobil, said he trusts his colleagues to vote on the merits of Tillerson’s nomination.

“I respect their integrity that regardless of having gotten donations, they can very well vote against that nominee if they feel that nominee doesn’t rise to the level they should live up to to get their vote,” Menendez told The Daily Beast. “I’ve received donations in the past and voted against the very interests of those entities, so I’m not going to believe that they are incapable of doing that.”

Rubio insisted the donations won’t affect his consideration of Tillerson’s nominations.

“When people contribute to my campaign, they support my agenda,” Rubio said. “I appreciate it when anyone agrees with my agenda, but as I’ve said, I have serious concerns about Mr. Tillerson’s nomination. I will do my part to ensure he receives a full and fair but also thorough hearing before the Senate Foreign Relations Committee.”

The 11 other senators on the committee who received donations either declined to comment or did not return a request for comment.