Washington (CNN) -- With South Dakota Democrat Tim Johnson's announcement this week that he will not seek re-election this year, the recent string of Senate retirements has the political class debating whether Republicans have a real shot at taking control of the upper chamber. But this biennial parlor game overlooks a stunning dynamic that has been developing on Capitol Hill over the past decade: massive turnover. Think back to late 2004, when a young hotshot from Illinois had just been elected to the Senate. National TV appearances led to obvious questions about his future political plans, but the senator-elect joked that he would finish out a full term, considering he was entering the upper chamber as its 99th-ranking member.
@highlight
With departures of long-serving members, a new Senate is emerging
@highlight
First Japanese-American woman and first openly gay woman joined Senate this year
@highlight
Record number of women now serve and growing number of senators have young children
@highlight
Aggressive conservatives are shaking up makeup of Republican side of the aisle
Republicans
Republican
Despite some of the nostalgia surrounding some of the old bulls who were more comfortable compromising and cutting deals, they believe the @placeholder conference is working harder than ever.