The company, which first used such labels for the midterm elections last year, said it is trying to provide users with original sources of information and prevent spoofed and fake accounts from fooling voters.
Many political candidates already have blue check marks to indicate that Twitter has confirmed that they are who they say they are.
The election labels go further and provide details such as what office a person is running for and where. They will also carry a small ballot box icon. The labels will appear on candidates' accounts and tweets, even if they are retweeted by someone else.
Twitter hopes its efforts will help people know when candidates are behind the words attributed to them. This could prevent someone from creating an account pretending to be a politician, for instance, or attributing a tweet to a candidate who didn't actually make the tweet.
Twitter, along with Facebook and other social media companies, has been under heavy scrutiny for allowing their services to be misused by malicious individuals and groups trying to influence elections around the world.
Facebook also verifies accounts for public figures and celebrities, while YouTube verifies official channels. But they don't go as far as adding election labels.
Labels will be used only for general election candidates and will start appearing once candidates have won their parties' primaries or have otherwise qualified for the general election ballot.
Twitter said it will apply the labels in House, Senate and gubernatorial races. Presidential candidates are not included in Twitter's new policies. The 2020 presidential candidates are already all verified and Twitter says if more join the race, they will get verified too. The company says it won't apply election labels to presidential candidates but may do so down the road.
Major presidential candidates already have blue check marks to indicate that Twitter has confirmed the accounts are legitimate. Many candidates for House, Senate and gubernatorial races have them as well.
Twitter said Thursday it will verify additional accounts, even if candidates do not seek them, by working with the nonprofit, nonpartisan Ballotpedia. Twitter said the verifications will happen on a rolling basis as candidates qualify for next year's primaries.