Electoral fusion is an arrangement where two or more political parties support a common candidate, pooling the votes for all those parties. By offering to endorse a major party's candidate, minor parties can influence the candidate's platform.
In several other states, notably New Hampshire, fusion is legal when primary elections are won by write-in candidates.
The cause of electoral fusion suffered a major setback in 1997, when the U.S. Supreme Court decided by 6-3 in Timmons v. Twin Cities Area New Party that fusion is not a constitutionally protected civil right.
In 1864 the Democratic Party split into two wings, over the peace question. The War Democrats fused with the Republicans to elect a Democratic Vice President, Andrew Johnson, and re-elect a Republican President, Abraham Lincoln.
Occasionally, popular candidates for local office have succeeded in being nominated by both Republican and Democratic Parties. In 1946, prior to the current ban on fusion being enacted in that state, Republican Governor of California Earl Warren (a future Chief Justice of the United States) managed to win the nominations of the Republican, Democratic, and Progressive Parties.
In the 1991 Louisiana gubernatorial election, controversial white supremacist David Duke, running as a Republican, unexpectedly made his way to second place in the state's infamous jungle primary. Many prominent Republicans endorsed his Democratic opponent Edwin Edwards. While not a de jure example of electoral fusion, it was an unusual example of both major parties joining against a candidate.
Fusion has the highest profile in New York, where it was a major weapon against Tammany Hall. Small parties significant in large part for their fused ballot lines include the Working Families Party, Right to Life Party, Liberal Party, Independence Party, and Conservative Party. Most judicial elections are won by candidates endorsed by more than two parties.
In the 2002 New York gubernatorial election, Andrew Cuomo got the New York State Liberal Party nomination, and was running against Carl McCall for the Democratic nomination. McCall had secured the Working Families Party nomination. Cuomo dropped out, and endorsed McCall. This led to the Liberal party not getting the 50,000 votes for governor that it needed for an automatic place on the ballot, and led to the Liberal party becoming defunct.