[ed. - Rob, dont mean to pile on but my thoughts were too long for the comments]
1. Leadership Vacuum
Whatever leadership vacuum in the GOP people seem to be going on about (especially given all the huffing and puffing about Rush Limbaugh as the new de facto leader), I think the House GOP's unanimous showing couldn't have happened by accident -- someone must have been shepherding. As much of a fan of spontaneous order as I am, someone was pulling the strings. This leadership vacuum, which was certainly real, goes back to at least last September when GOP leadership got behind Bush and still couldn't rally passage of TARP in the House. What's changed? Well, an election I guess.
Nate Silver has a point that this could have been the result of the roll call vote, which shames ambivalent caucus members into falling in line -- basically an information cascade. But where was this effect on TARP? And since most remaining Republicans are in safe seats, why would they care? I suspect this explains a few fence-sitters but not the rare showing of unanimity.
2. The Orphaned Tax Cuts
Yglesias may be right that Obama, for policy reasons, should've focused on getting the best deal his team wanted, and not trying to buy out Republicans. Because the end result was totally predictable based on what was offered and was politically shrewd to boot. No one really liked these "tax cuts"....except Democrats. It's probably deserved that anything that involves "taxes" and "cuts" is assumed to be part of the conservative Republican ideology. But this large share of the bill devoted to tax cuts are not the supply-side kind that right wing economists salivate over.
These tax cuts are tax rebates, in other words a bunch of checks that will go out. You may remember this plan from all the way back in 2008. And what was the result? A small, temporary blip in GDP and then it fell right back to trend. We know (and conservative economists especially know) these kinds of one-time rebates don't work(since 1820), especially in an environment of uncertainty and mounting budget deficits. In fact for all the talking points from Dems saying "we don't want to repeat the economic policies of Bush," they're doing a fine job of rehashing.
The tax cuts Republicans like are incentive-changing: preferably permanent, but sometimes temporary, changes to rates and application that change how people decide to order their economic arrangements. No one in the Republican leadership was asking for one time rebates, especially not for low-income and non-tax paying individuals. The tax cuts portion included in HR1 were drafted by Dem leadership, and championed by no one. What Obama got was a way to say he made an effort to compromise on the bill, done so in a way that most people wouldn't see the difference in what Republicans wanted and what they got. It was brilliant -- House R's look bad either way.
3. The GOP alternative
GOP leadership picked way too late in the game to get their shit together, but they did eventually and did not simply foot stomp their way to voting "no" (well, there was some foot stomping going on). Before the vote they offered their own alternative.
Some portions of it are basically right out of the Heritage Foundation proposal (I was there when it was being pitched). That's no big surprise. But it was so late that I don't blame Pelosi for calling the vote.
4. Heterogeneous Views
As Rob has aptly explained, there are plenty of legit economists who disagreed on how and whether a stimulus would work. Coming out of the gate, Obama and Biden and others said otherwise, and Greg Mankiw has some ideas why that is. But it simply wasn't true and it may have alienated GOP members early on.
5. My Stimulus
I've got my own thoughts on how a stimulus should be structured, and without belaboring this post, the basics are:
--The annual aggregate state sales tax is worth about $400B. The federal gov't buys out this sales tax for one year, and on day of passage, states suspend their sales tax. If you want people to spend, make it cheaper to do so, and go directly to the source. Consider phasing the tax back in next year instead of a sudden reinstatement.
--If employment is your primary goal, you have to operate on that margin instead of a roundabout one. Reduce the employer contribution to payroll tax by 50% for one year. This would cost about $200-250B
--Embrace the built-in, counter-cyclical (some would even say Keynesian) policies we already have. Unemployment insurance, food stamps, and Medicaid all cost more (because of increased demand) in downturns by design. They are also already targeted at the most needy. Unfortunately these burdens largely fall on states and they are running red all over. So increase federal support of these programs with conditions that they ease restrictions on eligibility and duration.