Is 2010 shaping up to be another 1994? According to the Real Clear Politics average of polls, Obama's job approval rating has been between 50 and 47 since the beginning of the year. Gallup puts Obama's approval at 47. To compare, at this same point in Clinton's first term, his job approval in the Gallup poll was 46 and would head up to 49 by the end of the month before dropping to 39 in September and end up back at 46 again the week of the midterm elections. So if the pattern holds, it looks like some of the conditions for 1994-like Republican gains are there.
But there are also reasons for long-term concern for Obama opponents. The unemployment rate for Jan-Nov 1994 varied from 6.6 to 5.9. The unemployment rate for the year to date has varied from 9.7 to 9.9. Obama has been keeping his approval ratings at about Clinton in 1994 levels during a much worse job market. And as Daniel Larison has pointed out (I can't remember when he posted it), Obama's approval ratings have been much more stable than Clinton's. I'm not sure exactly what all this means except that Obama's popularity has been holding up remarkably well given the labor market and that even a modest decline in the unemployment (say to the low 7s) could, absent some perceived foreign policy disaster, push Obama's job approval rating into the 50s and put him in a very strong position for reelection.
One of the things that jumps out at me about the relationship between the unemployment rate and a President's job approval rating is how context-dependent it is even absent foreign policy disasters like Iraq in 2006 or rally-round-the-flag effects due to events like Reagan getting shot. Reagan had high approval ratings for most of 1984, but the unemployment rate for most of the year was in the 7s - which isn't that good by the standards of the last thirty years. But it was alot better than the 10 percent or more unemployment of much of 1982. Probably just as important, the halving of inflation rate from 1981-1984 halted the erosion of the living standards of those who had jobs. Obama, after this recession, might also be running for reelection in a country with reduced expectations for what a "low" unemployment rate looks like.