[[Full Text of the United States Constitution|Article I, section 3]] of the [[United_States_Constitution|Constitution]] requires the [[United States Senate|Senate]] to be divided into three classes for purposes of elections. Senators are elected to six-year terms, and every two years the members of one class-approximately one-third of the Senators-face election or reelection. Terms for Senators in Class I expire in 2013, Class II in 2009, and Class III in 2011.<ref>[http://www.senate.gov/reference/glossary_term/class.htm] US Senate Reference</ref>
+
[[Full Text of the United States Constitution|Article I, section 3]] of the [[United_States_Constitution|Constitution]] requires the [[United States Senate|Senate]] to be divided into three '''classes''' for purposes of elections. Senators are elected to six-year terms, and every two years the members of one class-approximately one-third of the Senators-face election or reelection. Terms for Senators in Class I expire in 2013, Class II in 2009, and Class III in 2011.<ref>[http://www.senate.gov/reference/glossary_term/class.htm] US Senate Reference</ref>