Was Barack Obama’s first political gaffe the one that still haunts him the most?

When Barack Obama was elected back in 2008, he had already laid the foundation for a brutal first year and put his own agenda in peril.

How? By picking Joe Biden as his vice presidential running mate and stripping his party of an easy “hold” in the 2010 Senate race.

As a sitting US Senator himself, Obama’s own election had already put one Democratic seat in play. He can hardly be faulted for that.

But the president-elect wasn’t done.

Before his cabinet was locked in, Mr. Obama would also “pick off” Ken Salazar and Hillary Rodham Clinton.

In all, four of the most powerful and confident Democratic Senators had been taken out of play.

Imagine how the health care debate might have fared differently, with Senators Biden and Clinton championing the Democratic reform effort?

(Imagine, too, if Rahm Emanuel, Mr. Obama’s Chief of staff, had remained in the House, serving as one of the Democrats’ ranking leaders.)

Before the dust settles, Republicans could well pick up all four of these Senate seats: Colorado, Delaware, Illinois, and New York.

Was it smart for the President to weaken his own party’s congressional majority just as he was launching one of the most ambitious legislative agenda’s of the last quarter century?

Mr. Obama may have been convinced that these were the only possible choices to round out his cabinet.

But in hindsight, it may also prove to have been an incredible act of hubris.