The largely banned potential of fusion poitics

Some Maine Greens recently got in trouble with their state party for starting a Facebook page called Greens for Bernie Sanders. This was considered disloyal since the Greens are once again planning to run a candidate for president. In fact, however, there is a long history of crossover support by third parties and, in the 19th century, it was proving so successful that it was ultimately banned in all but eight states. Here is some Wikipedia background on the issue: 

Fusion politics

Electoral fusion is an arrangement where two or more political parties on a ballot list the same candidate, pooling the votes for that candidate. Distinct from the process of electoral alliances in that the political parties remain separately listed on the ballot, the practice of electoral fusion in jurisdictions where it exists allows minor parties to influence election results and policy by offering to endorse or nominate a major party's candidate.

Electoral fusion was once widespread in the United States. In the late nineteenth century, however, as minor political parties such as the Populist Party became increasingly successful in using fusion, state legislatures enacted bans against it. One Republican Minnesota state legislator was clear about what his party was trying to do: "We don't propose to allow the Democrats to make allies of the Populists, Prohibitionists, or any other party, and get up combination tickets against us. We can whip them single-handed, but don't intend to fight all creation." The creation of the Minnesota Democratic-Farmer-Labor Party made this particular tactical position obsolete. By 1907 the practice had been banned in 18 states; today, fusion as conventionally practiced remains legal in only eight states, namely:
Connecticut Delaware Idaho Mississippi New York Oregon South Carolina Vermont

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.

Fusion has sometimes been used by other third parties. For example, the Independent Party of Oregon cross-nominated five major party candidates, winning races for the U.S. Senate, Oregon State Treasurer, and the Oregon House of Representatives in 2008. The Libertarian Party of New Hampshire used fusion to elect four members, Calvin Warburton, Finlay Rothhaus, Andy Borsa and Don Gorman, to the New Hampshire state legislature during the early 1990s.

In 1864 the Democratic Party split into two wings over the question of whether to continue the American Civil War or back down and negotiate peace with the Confederacy. 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. Similarly, Allan Shivers won the 1952 nominations of both the Democratic and Republican parties in Texas (and had his name appear on the ballot twice, once for each party; Democrat Shivers handily defeated Republican Shivers in the general election).

In Milwaukee, Wisconsin, during the heyday of the Sewer Socialists, the Republican and Democratic parties would agree not to run candidates against each other in some districts, concentrating instead on defeating the Socialists. These candidates were usually called "non-partisan", but sometimes were termed "fusion" candidates instead.

Fusion has the highest profile in New York, where it was used as a major weapon against Tammany Hall. Most legislative and judicial elections are won by candidates endorsed by more than two parties.

The first fusion gubernatorial election was held in New York in 1854, in which the major party Whig candidate was supported in a fusion candidacy by eleven other political parties, among them the “Strong-Minded Women” Party, the “Anti-Rent” Party and the “Negro” Party.

Prior to 1958, Oregon practiced a form of fusion that required the state to list multiple nominating parties on the candidate's ballot line. Sylvester Pennoyer was elected Governor in 1886 and 1890 as a candidate of the Democratic and People's Parties. In 1906, 7 members of the Oregon House were also elected as candidates of the People's party and either the Democratic or Republican parties. 


Electoral Alliances

An electoral alliance may take the form of a bipartisan electoral agreement, electoral agreement, electoral coalition or electoral bloc. It is an association of political parties or individuals which exists solely to stand in elections. Each of the parties within the alliance will have its own policies, but will choose temporarily to put aside differences in favor of common goals and ideology. On occasion, an electoral alliance may be formed by parties with very different policy goals, who agree to pool resources in order to stop a particular candidate or party from gaining power.

Unlike a coalition formed after an election, the partners in an electoral alliance will usually not run candidates against each other, and will encourage their supporters to vote for candidates from the other members of the alliance. In some agreements where a larger party enjoys a higher degree of success at the polls, the smaller party will field candidates under the banner of the larger party, with the elected members of the smaller party sitting together with the elected members of the larger party in the cabinet or legislature. They will usually, but not inevitably, aim to continue co-operation after the election, for example by campaigning together on issues on which they have a common viewpoint.