The legislatures of 49 states are required to refer proposed constitutional amendments to the ballot for voter consideration. Most of the states (36 of 49) require legislatures to approve the amendments during one legislative session. An additional four states allow amendments to be passed during one or two successive legislative sessions, depending on how many lawmakers vote in favor. The remaining nine states require legislatures to approve amendments twice—once during one legislative session, and then again during the next legislative session. Delaware does not require constitutional amendments passed by the legislature to be referred to voters.
The two-session requirement means that a legislature can approve an amendment, and then, during the following session, reject the amendment or exclude the amendment from a floor vote.
Between the 2010 and 2018 legislative sessions, 62 constitutional amendments were approved during one legislative session in those states with two-session vote requirements. However, 21 of these constitutional amendments (33.9 percent) failed during the second legislative session.
An average of 0.5 constitutional amendments were referred to the ballot in each two-session state per year between 2010 and 2018. This compares to an average of 0.7 constitutional amendments per year that were passed in the first session and would have been on the ballot without the two-session requirement. The average for states where just one legislative session is required to refer an amendment was 1.6 per state per year. With the outliers of Alabama and Louisiana removed, the average in these states was 1.3 per state per year.
The two-session requirement means political variables—such as party control of legislative chambers and leadership—can change between sessions. These changes can influence whether an amendment fails to make the ballot despite receiving initial approval. When there was a change in party control of the legislature between legislative sessions, 90.0 percent of the constitutional amendments approved during the first session failed during the second session. When the same party kept control of the legislature between legislative sessions, 23.1 percent of the constitutional amendments approved during the first session failed during the second session.
Additional reading:
https://ballotpedia.org/Amending_state_constitutions
https://ballotpedia.org/Legislatively_referred_constitutional_amendment
Learn More
