Upon hearing that Bill Halter unexpectedly forced a runoff with Blanche Lincoln in Arkansas, I thought of the same thing as Willy. But I don’t think we’ll have our very own Bill Halter knocking off Claire McCaskill in 2012. (Obviously, things change in even 2 years, so don’t hold me to that.)

The big difference is that Arkansas is an overwhelmingly Democratic state, despite how it votes in presidential elections. Three out of four congressional representatives are Democrats. The US senators are both Democrats. The Governor and Lt. Governor are both Democrats. Out of 35 Arkansas state senators, 27 are Democrats. Out of 100 Arkansas state representatives, 72 are Democrats.

You might think this is immaterial in a Democratic primary, but that’s a large pool of potential challengers for a sitting US Senator, especially to challenge a US Senator who dithers on key Democratic issues like energy, health care, and financial regulation. In Missouri, the numbers aren’t as bad for the Democrats as they are for Republicans in Arkansas, but Republicans have a healthy majority in both houses of the state legislature, especially in the higher profile State Senate. None of the Democratic state legislators, nor even the Democratic congressmen, seem to me to have the statewide profile to reach for McCaskill’s Senate seat.

And the fact that Arkansas elects a lot of Democrats is also important; an ambitious Democratic legislator or statewide elected official has to like their chances in Arkansas, if they can figure out a way to overcome the opposition in a primary. In Missouri, defeating an incumbent is not the only incredibly difficult challenge; it’s the first step. That’s got to give a potential McCaskill challenger pause.

Finally, as much as we wring our hands about crappy votes that McCaskill has made in the past and continues to make, she’s a lot better than Lincoln [See here for why I struck that out], McCaskill is viewed more favorably by Democrats in Missouri than Lincoln is in Arkansas.

One area where Democrats in Missouri have managed to do well in the last two cycles is the executive branch, so if McCaskill got a challenge in 2012, you’d probably expect it to come from there. Attorney General Koster is probably the only one I could see doing it, although State Treasurer Clint Zweifel is certainly bright and driven enough to be a US Senator.

Then again, as I said at the beginning of the post, 2 years is a long time in politics, and if McCaskill’s numbers stay this far down, someone from her own side of the aisle might start thinking about going after her seat.