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.

In addition, Robert Byrd’s Senate seat from West Virginia and Ted Kennedy’s from Massachusetts could become vacant before 2010. Massachusetts Gov. Deval Patrick can’t appoint a senator, but West Virginia Gov. Joe Manchin can – and likely would appoint himself, or resign and be appointed in a political deal.

Sort of in this category is Arlen Specter, Pennsylvania’s five-term Republican senator who switched parties this spring. Although not appointed, he has been anointed by Obama and Gov. Ed Rendell as their man; both are demanding that fellow Democrats fall in behind him.

Here’s a breakdown of how each of these anointed senators looks today:

Specter: Making it through the Democrats’ 2010 primary is a big “if.” Beltway Democrats worry about his ability to hold off an aggressive challenge from U.S. Rep. Joe Sestak of Delaware County, who will be well-funded and who doesn’t have a lot of party-primary vulnerabilities – unlike Specter, who has many. Specter needs to assure Dems that his party switch was made on principle, not calculation. And he needs to show that his seniority and his White House support will help Pennsylvanians. The economy will not weigh heavily here; this election will be all about Arlen Specter.

Burris: A disaster. His only hope is to have such a crowded primary that, as the lone African-American candidate, he consolidates African-American support – but the Dems will be careful to make sure that doesn’t happen. Burris as the nominee means the seat is as good as gone for Democrats.

Gillibrand: Had a shaky start but is a talented, tough politician who is likely to steady herself and improve her position; she also has a first-rate team. Her close polls versus Rep. Carol Maloney are largely because she is unknown. But she is a fund-raising machine, will swamp Maloney with money and use that advantage to polish her image. Maloney will run an aggressive campaign and hit her where it hurts – on guns and tobacco – but Gillibrand will prevail. The economy won’t be a factor.

Bennet: Doesn’t seem in any danger of facing a primary, but is likely to have a tough general election because Colorado is a swing state. He needs to build up his image, introduce himself to voters (most of whom don’t know who he is) and show that he can get things done for Colorado. This is where the economy could matter; voters may punish the party in power if things haven’t improved. If voters think the economy is turning around, he’ll have a much easier time.

Kaufman: Ted always was a placeholder; he will pass in favor of Biden’s son, Beau. Yet Republican Rep. Michael Castle is looking strong to win the seat. Castle is running to cap a career and to avoid a tough re-election – and the tide may be with him.