Former Sen. Jon Kyl (R-AZ) will replace the late Sen. John McCain (R-AZ), it was announced on Tuesday, in a move that could have profound implications on everything from government funding fights to the current Supreme Court confirmation battle over Brett Kavanaugh.

In returning to Senate, Kyl brings with him years of previous legislative experience, strong relations throughout the GOP, and time working with the administration on the Kavanaugh nomination, for which he is serving as a proverbial sherpa. His likely vote in favor of confirmation strengthens the already-strong likelihood of it happening.

But Kyl also brings with him some ethical baggage, in the form of numerous high profile corporate clients with extensive business before the Senate body that he now re-joins.

Kyl, who has only committed to serve through this Congress—though he can stay on till the 2020 elections—retired in 2013. Almost immediately after, he joined the powerhouse Washington law and lobbying firm Covington & Burling where he has represented companies and trade associations in the defense, financial services, technology, and pharmaceutical industries.

Drug industry trade group PhRMA and a number of its member companies, defense contractors Northrup Grumman and Raytheon, and microchip manufacturer Qualcomm, have been among Kyl’s most prominent clients.

Kyl’s work for Covington clients has included advocacy on specific legislative proposals on which he could end up voting as a sitting Senator. For PhRMA, he has lobbied on a host of bills concerning the trade and regulation of prescription drugs. As Congress considers its next funding bill, Kyl will also likely be in a position to vote on appropriations for military programs such as the B-21 bomber, on which he’s lobbied for Northrop Grumman.

Kyl has also advocated for so-called DREAMers, the children of undocumented immigrants whose ability to stay in the country was thrown into doubt by the Trump Administration’s cancellation of the Deferred Action for Childhood Arrivals program. Kyl’s DACA lobbying, undertaken on behalf of the American Council on Education, Georgetown University, and former Washington Post publisher Donald E. Graham, could dovetail with Senate consideration of such a proposal this year as part of a deal to avert a government shutdown.

Kyl did not immediately return a request for comment.

In retirement from public office, Kyl has also been tapped for projects typically reserved for ex-lawmakers with respectable records. That’s included leading a probe into potential anti-conservative bias at Facebook. A spokesman for the company said that they were paying Covington for the work, though it was not revealed how much. An executive from Facebook is testifying before the Senate on Wednesday morning. Kyl is likely to be seated soon but it’s unlikely to happen before then; nor is it clear if he would be placed on the Intelligence Committee, which is conducting the hearing.

Kyl is also helping hand for confirmation fights. Before he was assisting Kavanaugh, Kyl was there to help Jeff Sessions be confirmed as Attorney General.

Kyl’s role as a Sessions ally may provide comfort to those fearful that President Trump wants to oust the AG and replace him with someone more deferential to his impulses to oversee and control federal investigations, including into Russia meddling in the 2016 election. So too may be some past comments that Kyl has made with respect to the president.

“I don’t like his style. I think it is boorish. I think he’s [his] own worst enemy. He could be much more effective if he were more politique, more diplomatic — of course that’s one of the things that people like about him — the fact that he isn’t that way. But I think there’s a happy medium," Kyl said in a local radio interview earlier this year.

Disclosure: Sam Stein's wife works for Facebook.