Of course. How is even The wave was coming, but the Democrats could've held onto the House by the skin of their teeth. If the GOP did as well as the Democrats did in 2006, they would end up eight seats short.
I believe that this is difficult to pull off once Scott Brown has been elected though. The best PODs would really be McConnnell and Chambliss losing in '08, which gives the Democrats a 61-seat majority before Specter switches. Republicans won't pour as much energy into Brown's campaign either, because that can't singlehandedly cripple Democratic legislation.
This is essentially just a "+1" post; Plumber has it exactly right.
If you go back through the fivethirtyeight.com archives during the run-up to the 2010 midterms, you'll see that there's a lot of sensitivity regarding the size of the "wave." Increase Democratic turnout by 1-2 points, and you can stem the tide of losses from "historic" to merely "awful", leaving the Democrats (barely) in control of the House.
The best way to do
that, IMO, is to increase base turnout -- that's what really drives mid-term elections, anyway -- and having the left fully behind Obamacare is probably the easiest way to do that. Plumber's POD (where the Dems have a 62-vote supermajority by the time of the Coakley-Brown race) is totally plausible; in that scenario, the White House doesn't bail on the so-called "public option," consolidating support among the universal-health-care Left.
I doubt it's possible for the right to hate Obamacare any more than they already do ITTL, so I don't see that an expanded health care bill would alter the trajectory of the 2012 presidential race beyond the usual butterflies. (To be fair, it
is a valid point of distinction between Obamacare and Romneycare, but since the GOP was already wedded to false attacks like 'death panels' and the like, it's hard to see a more nuanced attack gaining more traction in the Republican primary.)