Requirements to be a US Senator

Requirements to be a U.S. Senator are established in Article I, Section 3 of the U.S. Constitution. The Senate is the United States' higher legislative chamber (the House of Representatives being the lower chamber), containing 100 members. If you have dreams of becoming one of the two senators who represent each state for six-year terms, you might want to check the Constitution first. The guiding document for our government specifically spells out the requirements to be a senator. Individuals must be:

• At least 30 years old
• A U.S. citizen for at least nine years at the time of election to the Senate
• A resident of the state one is elected to represent in the Senate

Similar to those for being a U.S. Representative, the Constitutional requirements for being a Senator focus on age, U.S. citizenship, and residency.

In addition, the post-Civil War Fourteenth Amendment to the United States Constitution prohibits any person who has taken any federal or state oath swearing to support the Constitution, but later took part in a rebellion or otherwise aided any enemy of the U.S. from serving in the House or Senate.

These are the only requirements for the office that are specified in Article I, Section 3 of the Constitution, which reads, "No Person shall be a Senator who shall not have attained to the Age of thirty Years, and been nine Years a Citizen of the United States, and who shall not, when elected, be an Inhabitant of that State for which he shall be chosen."

Unlike U.S. Representatives, who represent the people of specific geographic districts within their states, U.S. Senators represent all of the people in their states.

Senate vs. House Requirements

Why are these requirements for serving in the Senate more restrictive than those for serving the House of Representatives?

In the 1787 Constitutional Convention, delegates looked to British law in setting age, citizenship, and residency or “inhabitancy” qualifications for senators and representatives, but voted not to adopt proposed religion and property ownership requirements.

Age

The delegates debated the minimum age for senators after they had set the age for representatives at 25. Without debate, the delegates voted to set the minimum age for senators at 30. James Madison justified the higher age in Federalist No. 62, stating the due to the more impactful nature of the “senatorial trust,” a “greater extent of information and stability of character,” was needed for senators than for representatives.

Interestingly, English law at the time set the minimum age for members of the House of Commons, the lower chamber of Parliament, at 21, and at 25 for members of the upper house, the House of Lords.

Citizenship

English law in 1787 strictly prohibited any person not born in “the kingdoms of England, Scotland, or Ireland” from serving in either chamber of Parliament. While some delegates to the Constitutional Convention might have favored such a blanket ban for the U.S. Congress, none of them proposed it.

An early proposal by Gouverneur Morris of Pennsylvania included a 14-year U.S. citizenship requirement for senators. However, the delegation voted against Morris’ proposal, voting instead for the current 9-year period, two years longer than the 7-year minimum they had earlier adopted for the House of Representatives.

Notes from the convention indicate that the delegates considered the 9-year requirement to be a compromise “between a total exclusion of adopted citizens” and an “indiscriminate and hasty admission of them.”

The U.S. citizenship requirement for senators developed into a subject of lengthy debate. As introduced in May 1787, James Madison’s Virginia Plan calling for a bicameral legislature made no mention of citizenship. In July, the convention’s Committee of Detail reported a draft of the Constitution in which Article V, section 3 included a four-year citizenship requirement for senators. On August 9, Gouverneur Morris moved to replace the four-year clause with a 14-year minimum. Later that day, delegates voted against citizenship requirements of 14, 13, and 10 years before passing the nine-year provision, making the Senate requirement two years longer than that for the House of Representatives.

The delegates considered the nine-year citizenship requirement to be a reasonable compromise “between a total exclusion of adopted (foreign-born) citizens” and an “indiscriminate and hasty admission of them.” 

While they were concerned that the Senate, more so than the House, not become subject to foreign influence, they did not wish to close the institution to otherwise well-qualified naturalized citizens. Irish-born delegate and future Supreme Court Justice Pierce Butler of South Carolina suggested that recent arrivals often remained dangerously attached to their countries of origin, a particular concern for senators whose role would include reviewing foreign treaties. Butler argued that naturalized citizens would need additional time to learn and appreciate American laws and customs before they could serve in government. James Wilson of Pennsylvania, however, argued that lengthy citizenship requirements “discouraged and mortified” those they excluded. Benjamin Franklin agreed with Wilson, suggesting that such a strict citizenship policy would hinder positive immigration and offend those Europeans who, like Thomas Paine, had risked their lives in supporting the Revolutionary War.  On August 13, Wilson moved to reduce the Senate qualification by two years. Delegates rejected his motion and confirmed the current minimum nine-year citizenship requirement by an 8 to 3 vote.

While over 70 foreign-born citizens have served in the Senate since 1789, the lone senator born outside of the United States to parents who were not American citizens as of 2022 is Mazie Hirono of Hawaii, who was born in Japan. There are also four other current senators—Michael F. Bennet, Ted Cruz, Tammy Duckworth, and Chris Van Hollen—who were born in other countries to American parents.

Residency

Recognizing the fact that many American citizens may have lived abroad for some time, the delegates felt a minimum U.S. residency, or “inhabitancy” requirement should apply to the members of Congress. While England’ Parliament had repealed such residency rules in 1774, none of the delegates spoke for such rules for Congress.

As a result, the delegates voted to require that members of the both the House and Senate be inhabitants of the states from which they were elected but placed no minimum time periods limits on the requirement.

The Senators’ Oath of Office

Unlike the far-shorter presidential oath of office, the Constitution does not specifically provide an oath of office for members of Congress, specifying only that members “shall be bound by Oath of Affirmation to support this constitution.” Every two years, following the midterm elections, one-third of the Senate takes an oath of office similar to the oath drafted in the 1860s by Civil War-era Senators intent on identifying and excluding traitors. However, the oath-taking tradition dates to the first session of the First Congress in 1789.

With the outbreak of the Civil War, the previously trivial, often festive, act of taking the oath of office became an enormously important and deadly serious affair. In April 1861, with the nation being torn apart by the Secession Crisis, President Abraham Lincoln ordered all civilian federal employees of the executive branch to take an expanded oath.

In December 1861, members of Congress who believed northern traitors posed as much of a threat to the Union as southern soldiers adopted Lincoln’s oath, adding an opening section ominously called the “Ironclad Test Oath.” Signed into law on July 2, 1862, the Test Oath required “every person elected or appointed to any office ... under the Government of the United States ... excepting the President of the United States” to swear that they had never previously engaged in any criminal or traitorous activity. Government employees or members of Congress who refused to take the 1862 oath would not be paid, and those determined to have sworn falsely were prosecuted for perjury.

The current oath of office for Senators, a much less-threatening version of the 1862 oath, has been in use since 1884 and reads: 

“I do solemnly swear (or affirm) that I will support and defend the Constitution of the United States against all enemies, foreign and domestic; that I will bear true faith and allegiance to the same; that I take this obligation freely, without any mental reservation or purpose of evasion; and that I will well and faithfully discharge the duties of the office on which I am about to enter: So help me God.”

Updated by Robert Longley