Sen. Charles Schumer, D-N.Y., asserts in today’s L.A. Times that it would be “impossible” for Republicans to take the U.S. Senate in 2012.

That’s not literally true, of course. Democrats currently control 53 seats (yes, that includes Joe Lieberman and Bernie Sanders), and there are certainly more than enough Democratic seats up for re-election that they could lose the Senate. But what about the individual races? Let’s step back a moment and look at some of them, at what is admittedly an early stage.

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• Republicans will be defending ten seats in 2012. Two are in blue states (Maine and Massachusetts), and two (Nevada and Arizona) are in states where there will be some competition on the presidential level. (I exclude Indiana on purpose.)
      Democrats’ two best pickup opportunities are probably Nevada and Massachusetts, against Sens. Dean Heller and Scott Brown, respectively. Both of those look like 50-50 propositions at best. So far, Dems lack credible candidates in the other two soft-target states. In fact, of those four, Democrats have only one top-tier recruit, and that’s Rep. Shelley Berkley of Nevada.
      Snowe will likely survive a primary challenge. There is a chance that Sen. Dick Lugar, R-Ind., will not. In that case, his seat becomes more competitive. But Lugar’s conservative primary challenger is a well-known statewide elected official, not some Christine O’Donnell or Sharron Angle type.
      There is also Texas, where Kay Bailey Hutchison is retiring. Republicans will probably nominate either their most popular statewide official, or a more conservative Hispanic former statewide official. Either way, it’s a winning formula in a Republican state.

• Democrats, meanwhile, will be defending 23 Senate seats in 2012. These are the ones I see within the realm of remotely competitive, in two categories:

  Incumbent Dem
  Nebraska* (Ben Nelson)
  Montana* (Jon Tester)
  Michigan* (Debbie Stabenow)
  Missouri (Claire McCaskill)
  Ohio (Sherrod Brown)
  Florida (Bill Nelson)

  Open seats:
  North Dakota*
  Virginia*
  Wisconsin*
  New Mexico*
  Hawaii*
  Connecticut

      I have starred the states where Republicans have one or more top-tier competitors in the race — not necessarily someone who will win, but someone you’d expect has at least as good a chance of winning there as any Republican.
      My thoughts on these: Nebraska and North Dakota are both gimmees. Connecticut, Florida, Hawaii, and Ohio are probably all a bridge too far. The rest are going to be interesting.

To sum up, Dems could gain anywhere from zero to two Senate seats this year. Republicans could gain anywhere from two to (a highly improbable) twelve. Probable net outcomes range from Dems+2 to Republicans +10.

So yes, contra Schumer, it’s all quite possible, and there’s even a decent chance of it happening. If support for President Obama sinks lower next year, I’d place bets on a net GOP gain of as many as six.

But that’s all conditional, and it’s really hard to say anything unconditionally this early. Recall that early in the 2010 cycle, it looked like Republicans were going to lose, not gain, Senate seats. Kentucky, Ohio, New Hampshire, and Florida all seemed doomed. Missouri, Louisiana and North Carolina were at least questionable. And then Arlen Specter switched parties.

No one expected the Republican blowout that later developed. So beware.