An excerpted passage from Krugman's new book is available on Slate. In this passage, Krugman explicitly advocates for an increase in "Progressive" partisanship now that Democrats have a clear edge in the electorate. He figures that Progressives should take a page from the Bush playbook and force their policy prescriptions down the throats of Americans by whatever means necessary- in essence, Progressives have (or will have) the reins of power to implement their policies, so they absolutely must do so. In the process, Krugman makes clear that Progressives should ignore and dismiss any sentiment opposed to their policy prescriptions. His sentiment is that Progressives are always 100% right (of course he ignores that "Progressives" have a variety of beliefs on any given policy and that there isn't really what you would call a consistent "Progressive" ideology).
As Damozel points out quite well at Buck Naked Politics, this is a recipe for disaster for the Democratic Party. Not only that, but she sees the implicit problem with Krugman's "ends justify the means" rationale:
Democratic elected officials should just impose a progressive agenda on the American people, whether or not there is really public support for it? Isn't that sort of kind of exactly the mistake that the Bush administration made----taking a reaction against Clinton for a massive realignment of public opinion and a mandate to push a neoconservative agenda?
I would hate to see a Democratic administration make the same mistake or fail to take note of a strong desire on the part of a large segment of the American public to dial back the partisan nastiness.
Damozel hits the nail right on the head: Democrats have received the support of a majority of Americans in recent elections not so much because all of a sudden the US public agrees with Progressives on everything as because the US public despises what the Bush Administration has done in forcing policies upon them that the public never voted for.
In addition to the moral problems with using a mandate on one issue as a mandate on all issues, the approach the Bushies have taken, and that Krugman advocates, ignores the third and, especially, the sixth rules of interest group politics. Specifically, any interest group that votes for the Democratic party in a given election does so for a very specific reason. If the Democratic Party wins the election and then shows itself to be as bad or worse than the Republican Party on the issue that attracted the interest group, then the Democratic Party will lose the support of that interest group in the next election. In the case of the 2006 elections, it was pretty clear that the Democrats won by securing the votes of Republicans and independents who were disillusioned with the Bush Administration's policies on things like the GWOT, civil liberties, executive power, and -importantly- partisanship, as well as (to a lesser extent) their lack of fiscal restraint.
If the Dems win the Presidency in 2008, it will likely be for similar reasons- hence the reason why the only Republican who would beat either Hillary or Obama right now is McCain, who alone amongst the Republican candidates has a reputation for bipartisanship. Similarly, Obama does better than Hillary in every conceivable matchup in the general election for the same reason: he can appeal to the middle in a way that Hillary can't. Someone voting for the Dems because they're tired of Bush's partisanship and abuse of executive power isn't going to be very happy with a Dem President who is equally partisan and abusive of executive power.
Another way to look at it: in 2006, the switch in the libertarian vote was critical to the Democratic victory, almost doubling its support of Dems between 2002 and 2006. Presumably, a Dem Presidential victory will rely in part on a similar or greater share of the libertarian vote. Krugman would reward that group's support (which was critical to Dems gaining power in the first place) by forcing upon them all sorts of policies that they would find unconscionable.
Krugman's argument, in the end, is not an argument for doing what is right or what is wrong. Instead, it is a rationalization for why Democrats should favor one interest group under its umbrella (ie, Progressives who agree with Krugman) over all others (such as disillusioned Republicans, political moderates, libertarians, and independents). Implicit in his argument is also the holier-than-thou belief that Progressives are different from conservatives in that Progressives care about the "public interest" rather than "special interests." This implication is a violation of the first rule of interest group politics: there is no difference between "special" interests and "public" interests: they're both just interest groups.
More at memeorandum.