There are no doubt many important issues that will be affected by tomorrow's elections in the U.S. According to the Economist (subscriber only), though, trade policy could experience some of the most noticeable effects:
The stalemate of divided government might well lead to better policy, particularly on the budget. But in one area Democratic control of one, let alone both, parts of the legislature would mark a clear change for the worse. Mr Bush's trade agenda would be stalled. And as the economy slows, the White House might then find it harder to hold off protectionist pressure from Capitol Hill.
Later, they get more specific:
The reason to worry is that Democrats' aversion to trade deals goes beyond thumbing their noses at Mr Bush. Lawmakers in both parties have become more sceptical about trade, but the Democrats are clearly the more protectionist party. A generation ago both the House and Senate contained large bipartisan groups of free-traders. In the House of Representatives, that coalition has long since fallen apart as the ranks of free-trade Democrats have dwindled. Democratic success in the Senate on November 7th may push the chamber in the same direction.
The Economist's view on the Republican-Democrat split on trade policy is probably the conventional one. However, it is unclear exactly how big the difference between the parties is. If the Democrats win big tomorrow, we may get a better sense.