The Encyclopedia of the First Amendment has two main case collections on election regulations:
Campaign Finance and Anti-Corruption Regulations, which includes summaries of 28 U.S. Supreme Court cases dealing with campaign finance, ranging from limits on expenditures, disclosure of contributors, and limits on contributions.
Election Regulations and Ballot Access, which includes summaries of 23 U.S. Supreme Court cases dealing with the election process and ballot access.
Other articles of interest:
Bipartisan Campaign Reform Act of 2002
Federal Election Campaign Act of 1971