I've been pointing out the similarities between the circumstances of Presidents Obama and Reagan for a while now. See an earlier post on this here.
The short version is both come in with inherited economic troubles that don't turn around miraculously in the first 24 months. Both replace deeply unpopular predecessors, and suffer from high expectations in comparison. And both set out to dramatically change the direction of national policy. Reagan suffered substantial losses in the House in his first midterm (26 seats lost), and Obama looks headed to similar if not larger losses in 2010.
So how is the analogy holding up? In approval terms, still quite well. The two continue to track rather well. Obama has occasionally been slightly below and recently slightly above Reagan's trend, but the parallel movement remains striking. Likewise, their relative location compared to other first term post-war presidents continues to drive home the point that these have been (so far) among the lowest approval ratings in the first 24 months.
Despite the similarity, I don't think the two presidents are metaphysically linked by fate. Both suffer from the economy and their large policy goals. At the moment, the economy is looking to have turned up sooner for Obama than it did for Reagan (who suffered until the very month of the midterm before the economy bottomed out and started to recover.) Obama has a more hopeful looking GDP trend, though his unemployment trend has not yet started down. (Political science finds that GDP is consistently a better predictor of midterm outcomes than is unemployment, despite the vastly greater emphasis on unemployment in public commentary.)
So I don't think the 2010 results are yet set in stone, nor that the track of Obama's approval is necessarily going to continue following Reagan's. Rather it has been driven by similar circumstances, and those circumstances appear to be diverging on the economy at least. Whether Obama's approval responds, and with what effect on midterm outcomes, remains to be seen. The politics is yet to finish baking.
Bonus Chart: The first term presidents through midterm but in separate charts rather than overlaid. Data are Gallup polls only to provide comparability over the decades.