Going through the article in this link - http://www.nytimes.com/2008/09/12/us/politics/12obama.html?_r=1&scp=1&sq=sharper%20tone&st=cse&oref=slogin - a couple of points come to my mind.
1) Plouffe thinks that starting to attack too early is not a good approach. He thinks it is best to start attacking a bit later in the game going into the debates. That strategy is sounding a little like Rudy's startegy to me, where he though he can start later in the game and start from Florida. Plouffe has done a great job in the primaries but he didn't have to deal with such a mean unscupulous attack machine as the republicans have. What he doesn't realize is that once Obama's image has been distorted by these attacks and a negative perception is created in the voters' mind it will be too late if the Obama tries to attack back at that stage. That appears like a loser hitting back.
2) The Obama campaign is too struck with the 'big picture' (like many ultra-cerebral democratic campaigns) of the campaign strategy and and things like forming a coherent message or attack campaign highlighting the top-level aspects of the campaign like 'Change' and 'Economy'. This leads it to ignore the very important tactical moves like hitting back hard at unjustified and untrue attacks from republicans which cause immense damage to Senator Obama's image.
3) The Obama campaign seems to think that it should bother responding to some attacks from the McCain campaign if they think it hasn't received widespread coverage in the interior/local papers in the competitive states. what it doesn't realize is that even if a handful of voters (well, a few thousand maybe) buy into every attack in the key states then it might prove to be pretty costly and also the beating will wear the sheen off the candidate and the sum of the attacks may add up to be a lot more than the individual parts.
The solution for all the three weaknesses pointed above is the same. Every small attack should be countered with the same gigantic force ,especially if it is one of the fabricated and falsified attack as that makes it easier to hit back on the other campaign's character. The reverse attack should come immediately after the commencement of the republican attack and should be very forceful. It should highlight the intentional deceptions/manipulations in the attack (there always is some from the republican side so that should be easy) and should be made out to reflect negatively on the character of the candidates behind the attacks. A strong forceful counter-attack ensures that the allegations don't stick to the candidate for long and wont create a permamnt stain on the candidate's image.
Read the other posts in the blog to get specific details on the counter-attacks.