Disclaimer. Don't rely on these old notes in lieu of reading the literature, but they can jog your memory. As a grad student long ago, my peers and I collaborated to write and exchange summaries of political science research. I posted them to a wiki-style website. "Wikisum" is now dead but archived here. I cannot vouch for these notes' accuracy, nor can I even say who wrote them. If you have more recent summaries to add to this collection, send them my way I guess. Sorry for the ads; they cover the costs of keeping this online.
Argersinger. 1980. A place on the ballot: Fusion politics and antifusion laws. American Historical Review 85:287-306.
Adoption of the Australian ballot (defined below) and related reforms in the late 1800s were not innocent institutional reforms: Republican state legislators adopted these anti-fusion laws with the explicit goal of preventing (minority) Democrats from fusing with smaller third parties. The (intended) result was the destruction of independent third parties.
In the late 18th century, Republicans passed a number of laws with a goal of making fusion difficult. The Australian ballot was one such anti-fusion law. Two other examples:
Argersinger presents a qualitative analysis with many interesting historical anecdoates to show that in the late 1800s--especially during the 1892 presidential campaign--these anti-fusion laws and the Austrialian ballot were adopted in an explicit attempt to keep the Democrats weak by undermining their attempts at fusion with smaller parties (notably the Populists). Eventually, the anti-fusion laws made things so difficult for third parties that smaller parties all but disappeared, with members formally joining the large parties.
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