Quick Summary
When a senator dies in office, the answer to who fills the seat depends almost entirely on which state they represented, because the Constitution leaves Senate vacancies to a patchwork of 50 different state laws. In 45 states the governor appoints a temporary replacement, in 5 states only a special election can fill the seat, and in several states the governor’s hands are tied to the departed senator’s political party. With the death of South Carolina Senator Lindsey Graham this weekend putting the process in the national spotlight, here is a complete guide to how Senate vacancies actually work, where the rules came from, and why the system still produces surprises more than a century after Americans started electing senators directly.
Where the Rules Come From
For the first 124 years of the republic, ordinary voters never elected senators at all. The framers assigned that job to state legislatures, reasoning that senators should answer to the states as institutions. That system produced chronic deadlocks, occasional bribery scandals, and seats that sat empty for months when legislatures could not agree. The Seventeenth Amendment, ratified in 1913, moved Senate elections to the people, and it also wrote the modern vacancy rule: when a seat opens up because of death, resignation, or expulsion, the state must hold an election to fill it, but the legislature may empower the governor to make a temporary appointment until that election happens.
Nearly every state took that offer. According to the Congressional Research Service, 45 states currently authorize their governors to appoint a senator when a vacancy occurs. The Senate Historical Office counts roughly 200 appointed senators since 1913, which means about one in every ten people who have served in the modern Senate first arrived without winning an election.
The Five States That Make Voters Decide
Five states refuse to let governors fill Senate seats at all: Kentucky, North Dakota, Oregon, Rhode Island, and Wisconsin. In those states, the seat simply sits vacant until a special election is held, leaving the state short one senator for months. Advocates of this approach argue that no one should sit in the Senate without facing voters first. Critics point out that a vacant seat leaves a state with half its Senate voice during what may be consequential votes.
The timing of elections varies everywhere else. Thirty-four states let the appointed senator serve until the next regularly scheduled general election, at which point a special election fills the seat for the remainder of the term. Many states add fine print: if the vacancy occurs less than eight months before a general election, the special election typically rides along with it, and if a vacancy occurs after candidate filing has closed, some states push the special election to within 90 days after the regular one.
When Governors Cannot Pick Whomever They Want
A growing number of states have added party protections, designed to prevent a governor from flipping a Senate seat to the opposite party through an appointment. Arizona, Montana, and North Carolina require the governor to appoint someone from the same party as the departed senator. Hawaii, Maryland, Utah, West Virginia, and Wyoming go further, requiring the governor to choose from a list of three names submitted by the previous senator’s state party. These laws emerged partly in response to history: governors have occasionally appointed themselves, appointed placeholders, or crossed party lines, and the 2009 scandal in which Illinois Governor Rod Blagojevich attempted to sell Barack Obama’s vacant Senate seat pushed several states to tighten their rules.
How It Works in Practice
Recent history shows the system’s range. When California’s Dianne Feinstein died in 2023, Governor Gavin Newsom appointed Laphonza Butler within days, and voters chose a permanent successor the following year. When Arizona’s John McCain died in 2018, Governor Doug Ducey appointed former Senator Jon Kyl, who served only a few months before a second appointee, Martha McSally, took over until a special election. And in South Carolina this weekend, Governor Henry McMaster must appoint a successor to Lindsey Graham while the state organizes a special primary to place the seat on November’s ballot, a compressed timeline that will test the state’s election machinery.
Appointed senators, it turns out, face a hard road: historically, fewer than half of appointees who seek election to the seat actually win it, a pattern political scientists attribute to the fact that appointees skip the coalition-building of a real campaign.
Why This System Matters
Senate vacancies can reshape national policy overnight. A 50-50 Senate can flip on a single death, which is why vacancy rules, once an obscure corner of election law, now draw intense partisan attention. Several states have changed their laws in the past two decades specifically because one party controlled the governorship while the other held the Senate seat. The stakes are rising as the Senate ages: the average senator is now well past 60, and the chamber has seen multiple in-office deaths in the past decade alone.
Key Numbers
45 states allow gubernatorial appointment, 5 require special elections only, 34 let appointees serve until the next general election, 8 states restrict appointments by party, and roughly 200 senators have been appointed since 1913.
FAQ
Who replaces a senator who dies in office? In 45 states, the governor appoints a temporary senator, and voters later choose a permanent one in a special election. In Kentucky, North Dakota, Oregon, Rhode Island, and Wisconsin, the seat stays empty until a special election.
Does the replacement have to be from the same party? Only in 8 states. Arizona, Montana, and North Carolina require a same-party pick, while Hawaii, Maryland, Utah, West Virginia, and Wyoming make the governor choose from a party-submitted list of three.
How long does an appointed senator serve? Usually until the next general election, when a special election fills the remainder of the term. In most states that means anywhere from a few months to about two years.
Can a governor appoint themselves to the Senate? Yes, in states without restrictions, though it is rare and historically unpopular with voters.
How is a House vacancy different? The Constitution requires House seats to be filled only by special election. No one can ever be appointed to the House of Representatives.
Editorial Note: This article was prepared using publicly available information from international news organizations and official sources available at the time of publication. Facts may be updated as authorities release new information.
Sources: