party leaders don't have very much power at all over backbenchers anymore. The days are long gone when newly elected members spent years quietly working their way up the seniority ladder and providing reliable votes for the party along the way. These days, they vote the way they need to vote, and there's very little anyone can do about it. Even threats to withhold fundraising are mostly empty. Party leaders need them more than they need party leaders, and everyone knows it.
Finally, there's the most obvious change of all: the decision by Republicans to stonewall every single Obama initiative from day one. By now, I assume that even conservative apologists have given up pretending that this isn't true. The evidence is overwhelming, and it's applied to practically every single thing Obama has done in the domestic sphere. The only question, ever, is whether Obama will get two or three Republican votes vs. three or four. If the latter, he has a chance to win. But those two or three extra votes don't depend on leverage. In fact, Obama's leverage is negative. The last thing any Republican can afford these days is to be viewed as caving in to Obama. That's a kiss of death with the party's base.
Obama may very well be a lousy negotiator. But honestly, that's just not a big factor here. He simply doesn't have much leverage of any concrete kind, and when it comes to soft leverage, his power is quite probably negative. That's life in modern Washington. Dowd needs to grow up and figure that out.