Washington ? “Were the expense of war to be defrayed always by a revenue raised within the year … wars would in general be more speedily concluded, and less wantonly undertaken.”

– Adam Smith, “The Wealth of Nations”

Evidence that a Democrat has read Smith’s great treatise against meddlesome government is as gratifying as it is startling. But perhaps there the evidence was last week, when Wisconsin Democrat David Obey proposed a $150 billion war surtax on incomes, ranging from 2 percent to 15 percent.

Democratic leaders, leery of making their itch to raise taxes even more conspicuous, reacted to Obey’s idea the way vampires react to garlic. But they are considering his proposal – which as chairman of the Appropriations Committee he can execute – to delay until next year action on the president’s request for $190 billion supplemental funding for the war. Congressional Democrats have heard growls from their base.

Those menacing sounds were provoked by Hillary Clinton’s and Barack Obama’s responses, in the Sept. 26 debate, to this question: “Will you pledge that by January 2013, the end of your first term, more than five years from now, there will be no U.S. troops in Iraq?” Their dusty answers were clear enough: No and no.

Because those responses were more or less sensible, they infuriated the party’s incandescent anti-war activists. Those activists thought that in the 2006 elections they had won for their party the power to end the war, but they have had to settle for increasing the minimum wage.

Surely it is not fanciful to imagine that in the fevered recesses of these activists’ minds there are thoughts of running, or at least threatening to run, an independent anti-war candidate in the general election. Most political professionals discount this possibility, saying that restive Democrats learned their lesson in 2000, when Ralph Nader’s 97,488 votes in Florida cost Al Gore the presidency. But another lesson of that episode is that a small number of intensely disaffected “progressives” can have momentous consequences. Hence they might have considerable leverage by threatening an insurgency.

Speaking of insurgencies, last week there were menacing rumblings from social conservatives about running an independent anti-abortion candidate if Rudy Giuliani is the Republican nominee. Perhaps if Hillary Clinton is the Democratic nominee, social conservatives will be terrified back into the fold, their fury assuaged by Giuliani’s repeated genuflections in the form of promises regarding what such conservatives care most about – judicial nominations.

But do not underestimate the temptation, to which the intense cohorts on Democratic left and Republican right are susceptible, to kick over their party’s furniture for the fun of it. The pleasures of moral purity are available to those who fancy themselves a small church militant in an unconverted world.

The multiplication of political media has infused politics with an extraordinary volatility. For example, in 2006, when Rep. Mark Foley, the Florida Republican, was incinerated in the House page scandal, his national name recognition went from essentially zero to the high 80s in six days.

Furthermore, increased volatility is guaranteed by the fact that Republicans are defending 22 of the 34 Senate seats to be contested in 2008. At least seven of the 22 are vulnerable – in Virginia, Maine, Minnesota, Nebraska, Colorado, Oregon and now New Mexico because of last week’s announcement that Pete Domenici is retiring after six terms. None of the 12 Democratic seats is as vulnerable.

If the election were today, Democrats probably would gain at least a dozen House seats. Then in 2010 there will be the census, followed by redistricting. So if the weakness of the national Republican brand seeps down the ballot to state legislative candidates the Republicans’ trek back to majority status will be steep.

Still, Republican leaders, noting that this remains a center-right country and that theirs is the center-right party, rejoice that some freshman Democrats who are not secure in their seats have had to cast awkward votes. For example, of the 61 Democrats who represent House districts that George W. Bush carried in 2004, 21 are freshmen, all of whom did organized labor’s bidding by voting for the “card check” process of organizing companies, which abolishes workers’ right to a secret ballot. That pleases unions but horrifies, and mobilizes, small-business owners.

The Republicans’ task is to delicately remind voters that the multiplication of such legislation arises from … well, as Adam Smith wrote: “It is not the multitude of ale-houses … that occasions a general disposition to drunkenness among the common people; but that disposition arising from other causes necessarily gives employment to a multitude of ale-houses.”