The 10th anniversary of the start of the Iraq War on Tuesday was a generally muted affair, reflecting the sustained national ambivalence about whether it merited the deaths of 4,488 Americans in uniform, the wounding of another 32,000 or the deficit spending that crested above $800 billion even before the last combat troops left 15 months ago.

That more than 100,000 Iraqi civilians have died — and that their country remains beset by sectarian tensions, terrorist bombings and political stalemate — helps account for the fact that the American public is split over whether the conflict was worth it: 46 percent said the war mostly achieved its aims, while 43 percent called it mainly a failure, according to a Pew Research Center poll from last weekend. That’s a statistical tie given the poll’s margin of error.

That the war has had a profound effect on the institution of Congress during the past decade is not up for dispute.

The invasion was the last major military operation granted an explicit, advance stamp of approval by Congress, and the lopsided and bipartisan votes of October 2002 remain the only time lawmakers ever authorized a preemptive strike on a sovereign nation. Those realities — and the fact that the main rationale for the war was to rid Iraq of weapons of mass destruction that turned out not to exist — are at the core of the current congressional hesitance toward new military entanglements.

It’s a bipartisan phenomenon that has to do as much with the revival of Republican isolationism as with the continuing conflict aversion among Democrats.

Capitol Hill’s collective doubt about the omnipotence of the intelligence community, and its interest in spending more generously on veterans than on almost anything else in this time of austerity, are two other clear imprints the Iraq War has put on the congressional culture.

Those policy shifts are tougher to quantify than the hard fact about what the war has done to the voting population of the Capitol. Only 32 percent of the lawmakers who voted on the war are in office today, a reminder that elections generate as much turnover as the term limits movement had hoped for. And among the newcomers are 15 Iraq War vets, who now account for one in six of the military veterans in the House. (There are none, yet, in the Senate.)

The roster of lawmakers who remain from a decade ago offers a crisp reminder about how the war debate helped usher in the current era of intense partisanship and ideological polarization. Of the 215 House Republicans who voted “yes,” 13 are now senators, including four who took seats away from Democrats in the first election after the invasion of Baghdad.

But only one of the 81 Democrats who voted for the war has gone on to any other higher office: Rod Blagojevich, whose turn as Illinois governor didn’t end so well. The roster will likely grow this spring because both Edward J. Markey and Stephen F. Lynch, the leading candidates for the open Massachusetts Senate seat, voted for the war.

The clear take aways: Backing the Iraq War was, from the start, part of the ante for potential advancement in the GOP. But being for the war as a Democrat proved to be a coin-flip sort of risk. The most obvious examples: John Kerry’s “yes” vote went a long way to his securing the 2004 presidential nomination and keeping that election close to the end; Hillary Rodham Clinton’s “yes” vote was one of the main reasons she wasn’t the nominee in 2008; and Joseph R. Biden Jr.’s “yes” vote helped get him on the ticket that year.

Things are only a little more clear-cut at the next level. Only eight of the 23 senators who voted “no” remain, but six are Democratic committee chairman and another, Richard J. Durbin of Illinois, is the party’s whip. Less than a quarter of the House Democratic “yes” voters are still around, an attrition rate that points at the decade’s steady decline in the moderate ranks of that caucus.

But more than half of the 126 Democratic “no” lawmakers remain; while the group is packed with big city and racial minority lawmakers with totally safe seats, it also includes six who went on to help the party secure its Senate majority and replenish the stock of progressive voices there.

Each of those Democrats has a seat on either the Foreign Affairs, Armed Services, Veterans Affairs or Homeland Security committees; the same is true for 10 of the GOP senators who backed the Iraq campaign in the House. In other words, one legacy of the last war is a Congress infused with the partisans positioned to plan, execute and recover from any next war.