In the U.S. Senate, the Minority Leader is elected, by members of his or her party, to organize the efforts of the minority party in office there. While the Minority Leader is usually senior, the position is not selected by seniority.
The incumbent, in 2010, is Mitch McConnell (Republican of Kentucky).
The Minority Leader has additional office funding, directs the Minority Whips, and often campaigns for candidates of his party.