On June 4, the Connecticut legislature passed HB 6580, which outlaws fusion unless both parties had polled at least 15,000 votes for one of the state statewide offices at the previous gubernatorial election. The bill passed the House on June 1 and the Senate on June 4. It also alters campaign finance laws. See this story, which is not accurate when it says the bill entirely bans fusion. “Fusion” means the practice of two parties jointly nominating the same candidate, so that his or her name appears on the November ballot with both party labels.
Assuming the Governor signs the bill and it takes effect, it is probably unconstitutional. States are free to ban fusion if they wish, but they cannot do so in a discriminatory manner. For instance, the Third Circuit struck down a Pennsylvania law in 1999 that permitted fusion between two large parties but not fusion between a large party and a small party, in Reform Party of Allegheny County v Allegheny County Department of Elections, 174 F.3d 305.
This is the same bill that temporarily had another provision, making it illegal for a party to have “Independent” or “Independence” in its name, but that provision was deleted from the final bill.
In 2010, the Working Families Party and the Independent Party each polled over 15,000 votes for some or all of the statewide state offices, so they retain the ability to engage in fusion. But the Libertarian Party’s highest statewide vote in 2010 was 14,748, and the Green Party’s highest was 10,328, so this bill eliminates their ability to engage in fusion. Those two parties don’t generally engage in fusion anyway, and the Green Party never does, but it is still unconstitutional to remove the ability from them and retain it for certain other parties. The bill also discriminates against newly-formed parties because they could not have met the requirement in the past gubernatorial election, because they didn’t exist then.