When General Motors CEO Mary Barra heads to Capitol Hill this week to testify in back-to-back House and Senate hearings about a switch defect that resulted in 13 fatalities and led to a recall of at least 2.6 million vehicles, she’ll be face to face with lawmakers who have benefitted from her company’s largesse.

From 1989 through the end of last year, GM made more than $12.3 million in campaign contributions to various politicians and groups, according to Influence Explorer data. For the current election cycle alone, Sunlight’s Real-Time FEC tracker shows that the General Motors PAC has doled out at least $481,775.

The largest overall recipient of GM contributions is Rep. John Dingell, an influential Michigan Democrat who will retire at the end of this year after nearly 60 years in Congress. GM has given Dingell $288,750, making the company his second-largest contributor ever. This cycle, GM’s PAC has given at least $10,000 to Dingell and his leadership PAC, Wolverine PAC.

Overall, however, GM’s contributions lean more toward Republicans, with $7 million going to GOP politicians versus $4 million to Democrats. Former President George W. Bush, whose administration approved a $13.4 billion auto bailout bill for GM and Chrysler (Bush successor Barack Obama committed much more money later), received $224,659 from the auto manufacturer.

Not surprisingly, GM gives generously to lawmakers from Michigan, where the company is headquartered. Influence Explorer shows the automaker contributing more than $3.3 million to federal and state politicians and groups from Michigan.

Two retired Michigan pols who remain on the influence circuit rank among the top recipients of GM campaign contributions, right behind Dingell and Bush: GM gave $125,500 to former Rep. Joe Knollenberg, a Michigan Republican who left the House in 2009 and is now a registered lobbyist for Strategic Government Affairs. The company also contributed $118,400 to former Sen. Spencer Abraham, another Michigan Republican who went on to lead the Energy Department under President Bush. Abraham now heads his own consulting group. For both Knollenberg and Abraham, GM was their highest overall contributor.

On Tuesday, GM’s Barra testifies before the House Energy & Commerce Oversight and Investigations Subcommittee, of which Dingell is a nonvoting member. Rep. Fred Upton, R-Mich., is on that subcommittee and is also the chairman of the full Energy Committee. He has received $68,250 from GM.

Before the committee hearing, Sen. Edward Markey, D-Mass., Sen. Richard Blumenthal, D-Conn., and Rep. Henry Waxman, D-Calif., are slated to hold a press conference with family members of the victims of the GM defect. Influence Explorer data show that Waxman, a ranking member of the Energy Committee, received a one-time donation of $3,000 from GM in September 2010. And Blumenthal serves on the Consumer Protection, Product Safety and Insurance Subcommittee, where Barra will testify on Wednesday. Campaign finance data in Influence Explorer suggests that Markey and Blumenthal have little to no financial support from GM.

GM employees weigh in, too. Real-Time shows that this cycle, GM employees have given at least $594,508.98 in predominantly low-dollar contributions to various candidates and groups. However, one large donation did come in from GM Senior Portfolio Manager Luis Roldan, who gave $15,000 to the DNC in September 2013.

As for Barra, in 2013, she gave a total of $1,435 to GM’s PAC and $1,000 to Rep. Gary Peters, a Democrat representing Michigan’s 14^th District, which covers eastern Detroit and its surrounding communities. Most of her political giving over the years has gone to the GM PAC, Influence Explorer shows. Her political contributions are included on a chart of campaign giving by Obama’s guests at this year’s State of the Union address.