Thanks to vacancies created by last fall’s election, then-president-elect Barack Obama faced the first dramas of his administration: Finding credible, re-electable bodies to fill those seats.

Remember the good old days of Illinois Gov. Rod Blagojevich and whether or not he could legally appoint someone to replace Sen. Obama? Then there was the near-anointment of Caroline Kennedy to replace New York’s Sen. Hillary Clinton.

After much controversy, Roland Burris took Obama’s Senate seat, N.Y. Rep. Kirsten Gillibrand replaced Hillary, Vice President Joe Biden’s former chief of staff, Ted Kaufman, took his place in the U.S. Senate, and Michael Bennet of Colorado now sits in Interior Secretary Ken Salazar’s Senate chair.

The 17th Amendment to the U.S. Constitution established the direct election of U.S. senators. Each state legislature is empowered to create a system in which a governor appoints a replacement to complete a Senate term or to serve until the next special election.

Only Oregon, Massachusetts and Wisconsin do not allow their governors to appoint, thus requiring special elections. Oklahoma requires a special election with a limited exception.

Alaska, Arizona and Hawaii require their governors to appoint a replacement from the same party as the departing senator; Utah and Wyoming require their governors to appoint an interim senator from three names provided by the party with the vacancy.

Since the 17th Amendment’s adoption in 1913, 184 Senate vacancies have occurred due to deaths, expulsions or resignations. Of the 184 replacements, 64 chose not to run in the next election, 34 lost the subsequent election and 22 lost their party’s nomination; only 60 went on to win the voters’ support.

Of the four latest appointees, Delaware’s Kaufman has said he will not run; New York’s Gillibrand and Colorado’s Bennet will run. Illinois’ Burris has not announced his plans. Continued...