I'm not sure about the gerrymandering theory: the Senate isn't gerrymandered, but people seem to believe that it isn't just the House that has become more polarized. There are other causes at work.

Dr. Dresner,

Today, liberal Democrats oppose trade expansion and relatively open immigration because they fear the effects on unions and the working class. Conservative Republicans oppose trade expansion and relatively open immigration because of fears about global interdependence and the loss of sovereignty.

Except that I know plenty of conservative Democrats (think former Sen. Fritz Hollings (D-SC) who were also very anti-trade expansion, although fairly pro-immigration. In the South, at least, the Republicans who are winning seats now are more pro-trade expansion than the Democrats whom they replaced. Look at North Carolina and Florida's Republican senators voting for CAFTA, despite the two states being textile and sugar states. Conservative Dems like Sen. Landriau are against.

Also look at how the liberal Repubicans, like Maine's two senators and Sen. Specter, voted against CAFTA.

Your hypothesis, at least as it relates to trade expansion, is contradicted by the facts. Liberal Republicans and conservative Democrats in the Senate were much more likely to vote against CAFTA than conservative Republicans.

Not to be churlish here, but I have to point out that the "man bites dog" coalitions on environmental policy, Darfur, prison conditions and so forth haven't really accomplished very much yet.

I'm glad some issues are being raised, and discussed, and that there are some politicians secure enough of their interest group support to approach members of the other party as if they were not afraid of picking up cooties. Maybe there are portents of the future here. But maybe not. The unconditional priority of the largest, best-funded and best organized interest groups is election campaigns, by definition the least promising forum for advancing bipartisanship. And since most elections are low-turnout affairs in constituencies too big for politicians to communicate with voters except through expensive paid media, interest groups that can pay the bills and mobilize people to get to the polls still call the shots, except on the issues they don't care about.

How about this explanation:

Views on social issues have caused Democrats to become ever-weakening in rural and farm states. They still have a decent chance of picking up Senate seats, though. In order to offset their growing disconnect on social and other issues from the farming areas, they have switched to the McGovern (D-SD) strategy: farm subsidies above all. (Back at home, he, like other farm state Democratic senators, was mostly known for bringing the farm pork.) Since they can't move off of the polarizing social issues-- that's a lot of what brings in the national money-- they have to continually increase the amount of farm subsidies they favor in order to increase their support in rural areas. (Note how, e.g., Sen. Clinton is a big supporter of various farming subsidies in order to placate upstate New York.)

Rural Republicans can rely on their other issues, and are slightly more immune to the pressures, though they are still there.

And then there's bipartisan trade expansion issue number two:

Democrats are willing to support free trade when there's a Democratic President, but not when there's a Republican. Republicans will give more support when there's a Republican President, but will still support otherwise. So of course trade expansion looks more bipartisan when there's a Democratic President. The reverse is true about immigration: you need a Republican President to propose an amnesty, which Democrats will eagerly go along on.

I don't think that is quite right, John. Many Democrats supported Clinton on NAFTA when they thought his Presidency would be wrecked if he couldn't get it through. They weren't happy about crossing the unions, though, and every subsequent trade issue that came up saw progressively fewer Democrats on the side of trade liberalization.

Conversely many of the business organizations with an interest in freer trade already have what they wanted. Liberalizing trade in farm products doesn't mean anything to them if they don't trade in farm products, and most of them don't. So Republicans face less pressure than they used to from free trade interests. Perhaps even more important is that Ronald Reagan was a thoroughgoing free-trader -- support for reducing trade barriers was one of the positions he didn't change when he changed parties in the 1950s. The elder Bush ran on inertia in this as in so many areas, but the younger Bush is driven by straight electoral considerations. Right now, these do not favor free trade, and so Congressional Republicans face no White House pressure to resist protectionist appeals from local interests desiring to suppress foreign competition.

Zathras:

Try searching for information on cotton subsidies and the WTO ruling, as I mentioned. Or the President's other recent statements, such as the G8 one about cutting agricultural subsidies. Or the way that the President twisted many, many arms to get fast-track approved (Rep. Robin Hayes (R-NC), was one of the last votes for it, in his first term replacing a retiring Democrat in a protectionist district-- but won reelection anyway), and is twisting arms about CAFTA right now.

The idea that the Congressional Republicans face no White House pressure to resist protectionist appeals is ridiculous. A more accurate statement, perhaps, is that the White House has acceded to demands from Congressmen to water down trade deals to get votes necessary to pass things, and that that has emboldened Congressmen to ask for more concessions. In the long run, yes, that is a problem. But if the trade deals wouldn't pass without those concessions, there's a deeper problem.

The bipartisan hypothesis offered by Dr. Drezner is still ridiculous, since liberal Republicans and conservative Democrats were more likely to vote against CAFTA than conservative Republicans. Indeed, conservative Republicans were quite likely to vote against parochial state interests.

Rollcall

Consider the states where the senators did not vote identically. In every single case, where they were the same party the more conservative/less liberal senator voted Yea while the more liberal/less conservative voted Nay, whether they were both Dems (CA) or both Republicans (AL, SC). In every case where they were of different parties, the Republican voted Yea and the Democrat Nay.

Different parties:

Colorado - Allard Yea, Salazar Nay. Salazar is a member of the Centrist Coalition.

Indiana - Bayh Nay, Lugar Yea. Bayh is a member of the Centrist Coalition.

Iowa - Grassley Yea, Harkin Nay.

Minnesota - Coleman Yea, Dayton Nay.

Nevada - Ensign Yea, Reid Nay. (Reid is traditionally a moderate, though also Senate Minority Leader right now.)

Rhode Island - Chafee Yea, Reed Nay.

Vermont - Jeffords Yea, Leahy Nay. (Jeffords a former Republican now independent, harder to classify.)

Both Republicans:

Alabama - Sessions Yea, Shelby Nay. Sen. Shelby is a former conservative Democrat party switcher, and a member of the "Senate Centrist Coalition." Sen. Sessions is more conservative.

Pennsylvania - Santorum Yea, Specter Nay. Specter is a moderate Republican, Santorum more conservative.

South Carolina - DeMint Yea, Graham Nay. DeMint is more conservative.

Both Democrats:

California - Boxer Nay, Feinstein Yea. Boxer is more liberal.

Connecticut - Dodd Nay, Lieberman Not Voting. Dodd is more liberal.

Delaware - Biden Nay, Carper Yea. Biden is more liberal.

Republican opposition to CAFTA can be almost entirely reduced to parochial interests-- specifically sugar.

John, your last and I gather main point doesn't contradict anything I said. Naturally I do not mean this as a criticism. Parochial interests with the ability to direct cash to campaigns or voters to the polls, or both, have a strong position when most Congressional elections are low-turnout affairs in districts large enough to require candidates to campaign using paid media. The sugar lobby is certainly one such interest, though historically it has had strong defenders on both sides of the aisle.

You are correct that the White House made a major effort to get fast-track, reasoning that its approval showed an improvement from the performance of the Clinton administration. As to the other examples you cite, I do not yet detect a great deal of arm-twisting on CAFTA, though I would be glad to be proven wrong; with respect to cotton subsidies, talk is cheap. By the time anything decisive will need to be done about these Bush will be on his way out of office. All he did at the G-8 was tell people with a stake in Doha -- notably his own USTR and Deputy Secretary of State -- what they wanted to hear. I'll believe it was more than that when I see action.

I contend that politics isn't a line defined by two points, but a trinagle (or a circle both of which are) defined by three points: liberal, conservative, and socialist. By "liberal" I mean classically or neo-liberal, favoring liberty, not equality, as its defining principle. Both US parties have spent the past quarter-century as liberal hybrids, one a liberal-conservative party, the other a liberal-socialist party. The so called moderates, were often just the liberal wings of both parties, who could agree on free trade and other issues. But of late, with the growth of the genuine conservative and socialist blocs in either party, untainted by liberalism, they can find common ground in their illiberalism. For example, conservatives can be paternalistic, and in so doing, find common cause with socialists. Though their motives for acting as they do may differ, and some issues will certainly be sources of conflict, the issues and the ideas that cause conflict will change