The Senate is a Byzantine institution. Its informal practices and old-boy networks are practically inscrutable to outsiders. Yet there are periodically reoccurring events that offer an opportunity to better understand how senators allocate power among themselves.

Consider Sen. Orrin Hatch's, R-Utah, recent announcement that he will retire at the end of this year. Hatch's decision caps a seven-term career in the Senate and upends the power structure among Republicans heading into 2019. The contest to succeed him as the top Republican on the powerful Finance Committee will shape the GOP's position on healthcare, entitlements, and tax policy, and help determine what the party can accomplish in the time remaining in President Trump’s first term in office.

Hatch's exit also kicks off a game of musical chairs that will affect a number of other panels beyond the Finance Committee. While Republicans informally follow the principle of seniority when selecting committee chairmen and ranking minority members, the party’s Conference Rules make clear that the top Republican need not be the panel's most senior member. The rules stipulate, “the Republican members of each standing committee at the beginning of each Congress shall select from their number a chairman or ranking minority member, who need not be the member with the longest consecutive service on such committee, subject to confirmation by the Conference.”

One notable example was the mid-1980s dispute between Sens. Jesse Helms, R-N.C., and Richard Lugar, R-Ind., over the ranking member position on the Foreign Relations Committee. After the GOP lost control of the Senate in the 1986 midterm elections, Helms decided to relinquish the top Republican spot on the Agriculture Committee, which he previously chaired, to claim the ranking member position on the Foreign Relations Committee (as he was the most senior Republican on the panel).

Yet Lugar also asserted a claim to the top position by virtue of the fact that he had chaired the committee in the previous Congress.

Pursuant to the Conference Rules, all of the Republican members of the committee, with the exception of Helms, voted to allow Lugar to retain his position as ranking member. Helms subsequently challenged their decision in the full Conference (which must ratify the panel's decision), staking his claim on the principle of seniority.

Helms asserted that failure to make him the top Republican would end seniority as the guiding principle in the committee assignment process. His argument was received favorably, even among more liberal Republican senators who were not predisposed to support the conservative Helms.

On Jan. 20, 1987, the Republican Conference voted 24-17 in favor of Helms. The conference also passed a resolution stating that the decision to allow Helms to claim the ranking member position was necessary “in order to preserve the vital principles of party unity and seniority.”

In the mid-1990s, the Republican Conference adopted various reforms to their Conference Rules, including imposing a six-year term limit for committee chairmen and ranking minority members. (The rule has been interpreted to mean that members are limited to six years of “chairman time” and six years of “ranking member time,” for a total of 12 years).

While the Helms-Lugar precedent still governed the process by which the Conference selected its committee leaders, imposing term limits on chairmen and ranking members created a new possibility. Specifically, the top Republican on a committee could now be “termed out” and thus forced to relinquish the top spot on a panel if he or she exhausted their chairman or ranking member time and Senate control did not flip.

In that scenario, another Republican would assume the top spot on the panel, effectively bumping the more senior senator. However, the outgoing Republican still technically maintained any chairman or ranking member time that they had not used previously. Consequently, under the Helms-Lugar precedent, the senator would be entitled to bump the incoming top Republican if Senate control flipped.

Notwithstanding the Helms-Lugar precedent, the use of seniority as the sole governing criteria in the committee selection process has weakened in recent years.

For example, Judiciary Committee Republicans considered denying Sen. Arlen Specter, R-Pa., the chairmanship of that panel after the 2004 elections. They were concerned about Specter's views on social issues and how those views would impact President George W. Bush’s Supreme Court nominees during the upcoming Congress. Specter was eventually allowed to claim the gavel, but only after assuring his fellow committee members that he would support the president’s judicial nominees. Henceforth, ideology would be taken into consideration informally, along with seniority, in selecting a committee's top Republican.

While Specter's experience assuming the Judiciary Committee chairmanship reaffirmed the use of seniority by the Republican Conference, albeit on a weakened basis, Sen. John Warner’s, R-Va., attempt to claim the ranking member position on the Environment and Public Works Committee after the 2006 elections demonstrated that seniority may not always be followed in the Senate.

Warner asserted a claim to the top Republican spot on EPW due to his seniority on the panel. Sen. James Inhofe, R-Okla., also asserted a claim to the position based on the fact that he served as the top Republican on the panel in the previous Congress and that he still had six years of ranking member time remaining under the term limits rule. Warner eventually dropped his claim to the ranking member position, under pressure from Republican leaders eager to avoid a potentially disruptive challenge to the seniority principle.

The Warner-Inhofe dispute established a new, un-adjudicated precedent that essentially clarified the application of the term limits rule to the Helms-Lugar precedent. Under this new precedent, it was assumed that a senator would be allowed to finish their entire term (defined as all of the chairman and ranking member time they were permitted under the rule; 12 years, if served concurrently) once they started. In short, they couldn’t be bumped by a senator more senior who had chairman or ranking member time remaining.

Senate Republicans established precedents a few years later that contradicted the Warner-Inhofe precedent. The top Republican position on the Judiciary Committee was vacated after Specter switched parties in 2010. Sen. Chuck Grassley, R-Iowa, was the next most senior Republican on the panel and thus in-line to take over after Specter. However, Grassley was serving at the time as the ranking Republican on the Finance Committee and wasn’t prepared to move to Judiciary. Sen. Jeff Sessions, R-Ala., was the next most senior Republican on the panel after Grassley, and thus eligible to assume the ranking member position.

Grassley and Sessions worked out an informal understanding that Sessions would step aside after the 2010 elections and allow Grassley to assume the ranking member position if the Republicans did not win a majority in the Senate.

A similar situation occurred on the Budget Committee when Sessions agreed to step aside for Sen. Mike Enzi, R-Wyo., who was the more senior member on the panel, even though Sessions had already started his time as Budget’s top Republican.

These conflicting precedents are illustrative of the fact that nothing is ever straightforward in the Senate.

James Wallner (@jiwallner) is a contributor to the Washington Examiner's Beltway Confidential blog. He is a senior fellow at the R Street Institute. Previously he was a Senate aide and a former group vice president for research at the Heritage Foundation.

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