Which Potential Independent Candidate Could Take Support Away From Obama?

[True Federalist (진정한 연방 주의자)]

Of the people who plausibly might run, none.  There's not much point in running a campaign to the left of Obama when the GOP is practically a lock to retain the House and is favored to retake the Senate.  Potential center-left opponents occupying the same political space as Obama are going to wait until 2016.

There aren't any centrist politicians who could pull off a run except possibly Michael Bloomburg, but I can't see him running.  He had his chance and he didn't take it.

If anyone tried to run a Perot-style insurgency, it would likely hurt Romney far more than Obama.

That said, I don't think Romney has anything to fear either.  It's too late for a creditable third-party run to begin.

[True Federalist (진정한 연방 주의자)]

While there are quite a few people who conceivable could act as a spoiler for Obama, there is zero indication that any of them are a "potential independent candidate".

[True Federalist (진정한 연방 주의자)]

There's not much point in running a campaign to the left of Obama when the GOP is practically a lock to retain the House and is favored to retake the Senate.

Yeaah, we'll see about that.

The Dems would need the economy to do much better than it is likely to for them to have any realistic chance.

As for the Senate, the GOP only needs to win 13 or 14 of the 33 seats up this year to retake the Senate.  2006 was a very good year of the Dems.  2012 will not be as good.

Here are the seats I see as either being in play or are certain to switch.
Florida is a tossup.
Maine is a double tossup since King has refused to indicate which party he would caucus with.
Massachusetts is a tossup
Missouri is lean Republican.
Montana is lean Republican.
Nebraska is a safe Republican pickup.
Nevada is lean Republican.
New Mexico is lean Democratic.
North Dakota is lean Republican.
Ohio is lean Democratic.
Virginia is a tossup.
Wisconsin is lean Republican.

Assuming that tossups toss as holds. The above list is still a five seat Republican pickup, giving them a 52-48 hold of the Senate.

While it is possible for the Democrats to retain the Senate, I'd place their chances of doing so as around 1 in 4.