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.
Army Ranks are more than just who salutes whom. Army rank is a badge of leadership. The other pay categories are W for warrant officers and O for commissioned officers. Some enlisted pay grades have two ranks. The Army has the ranks of corporal and specialist at the pay grade of E-4. A corporal is expected to fill a leadership role and has a higher rank than a specialist even though both receive the same amount of pay. Rank images and info from Defenselink.mil and www.perscom.army.mil.