When historians look back on our current time, what are they going to conclude signaled the end of our current economic expansion, one of the greatest in the history of America? We’re starting to have the feeling that they are going to date it with the accession of the Democratic Party via the 110th Congress. That is certainly the portent in the latest dashed hope of the Bush administration, a plan to adjust, if only modestly, a rule that hurts American airline passengers by barring international investment and involvement.

The rule bars non-citizens from owning greater than a 25% voting share in any domestic airline and requires that the top executives and a majority of the boards of these airlines be American. The federal secretary of transportation, Mary Peters, announced yesterday that her department was withdrawing a proposal to change the rule.

“It was clear from reviewing the comments that the Department needs to do more to inform the public, labor groups and Congress about the benefits of allowing more international investment,” Ms. Peters said in a statement. The AFLCIO promptly hailed the Bush administration’s surrender as a victory, crediting “strong and unified opposition from America’s transportation unions.” What it really means is that at a moment when America’s air carriers need all the capital they can muster, the Congress is a roadblock to their raising capital.

Nor is this an isolated case. Congress last month failed to pass a trade deal with Vietnam, in part because Democrats opposed it. The Democrats don’t seem to be talking about putting President Bush’s expansion of legal immigration at the top of their congressional agenda, though the right way to view the campaign against immigration is as part of the new protectionism. Or to put it another way, the instinct to protectionism isn’t only a Democratic fault. It has its adherents in the Republican right wing. But it is the Democrats who have become the primary purveyors of the new protectionism.

The irony is clear. The Democrats are up on their high horses at the moment over Ambassador Bolton. Senator Smoot Schumer — co-author with, of all people, Paul Craig Roberts of a protectionist piece in the New York Times a few years ago — averred that Mr. Bolton “seems to have a ‘go it alone’ attitude at a time when we need the nations of the world on our side.” Senator Kerry reckons Mr. Bolton “helped isolate the United States.” While this kind of malarkey is being uttered, the Democrats themselves are taking protectionist steps to wall America off. Let them go read how the prosperity of the 1920s was cast off and how the Great Depression was ushered in, opening one of the darkest chapters in our country’s history.