In 2012, candidates needed either one percent or 500 signatures (whichever was lower) from Democrats in each of the state's 50-plus congressional districts. They had two months to do so -- which, particularly if you're hoping to keep expenses under $5,000, is a time crunch. Other states work similarly; some don't.
A contemporary definition of rank-and-file is prevalent in labor union vernacular when referring to general membership and not union leaders. Rank-and-file generally means the employee doesn't occupy a high-level position within the organization.
File, a string, is to point out a file. The contents of this file are included as is, at the position of the directive. Include files are typically used for record and macro definitions that are shared by several modules. It is recommended to use the file name extension .hrl for include files. File can start with a path component $VAR, for some string VAR.