Parties also shape the organization of government by augmenting the ties between the states and the national government in our federal system. State parties play a prominent role in selecting candidates for President and Vice-President through winner-take-all state-level primaries. Members of the U.S. Congress run as party candidates on the state level. U.S. Senators recommend state party loyalists as nominees to the federal District courts in that state. Party loyalty is also frequently a consideration in upper-level appointments to federal bureaucracies. Parties thus often serve as a career network through which candidates and political professional can progress from state-level to national-level political work.