Party in the Street: The Antiwar Movement and the Democratic Party after 9/11, by Michael T. Heaney and Fabio Rojas, Cambridge University Press, 245 pages, $29.99

Party in the Street is a deceptively cheery title for an autopsy. In this book, the social scientists Michael T. Heaney and Fabio Rojas dissect the remnants of "the second most significant antiwar movement in American history" after Vietnam—the post-9/11 effort to restrain the American war machine.

In the years after the September 11 attacks, Heaney and Rojas write, peace activism became "truly a mass movement": From 2001 through 2006, there were at least six anti-war demonstrations that drew more than 100,000 protestors, "including the largest internationally coordinated protest in all of human history" in February 2003.

The authors brought teams of researchers to most of the largest national protests from 2004 to 2010, and gathered reams of survey data from more than 10,000 respondents. Early on, they noticed substantial overlap between anti-war agitation and affiliation with the Democratic Party. That "party-movement synergy" helped the war opposition to expand dramatically during the administration of George W. Bush. It also, eventually, contained the cause of its undoing under Barack Obama. "Once the fuel of partisanship was in short supply," Heaney and Rojas note, "it was difficult for the antiwar movement to sustain itself on a mass level."

The book begins with a scene from the anti-war campaign's height: Saturday, January 27, 2007, on the National Mall in Washington, D.C. The occasion was a rally organized by United for Peace and Justice (UFPJ), the leading anti-war coalition during the Bush years. An estimated 100,000 protesters turned out to "tell the new Congress: ACT NOW TO END THE WAR!" In a fit of irrational exuberance, several hundred protesters actually tried to rush the Capitol while the crowd chanted "Our Congress!" at the police officers blocking their way.

On that sunny winter day, the movement's legions looked ready to convert their ire into genuine policy change. In the 2006 midterms, not three months before, Democrats had taken control of Congress for the first time since 1994, in large part because of national discontent with the Iraq War. As Rep. Lynn Woolsey (D–Calif.), put it from the podium: "We have an antidote to this insanity…It is what you sent us to do last November!" The following Monday, UFPJ unleashed 1,000 grassroots activists on the Hill to swarm their representatives, demanding they support withdrawal resolutions and join the "Out of Iraq Caucus."

But that rally turned out to be the high-water mark; the tide soon receded and within a few years the sea itself dried up. "At exactly the time when antiwar voices were most well poised to exert pressure on Congress, movement leaders stopped sponsoring lobby days," the authors recount. From 2007 to 2009, "the largest antiwar rallies shrank from hundreds of thousands of people to thousands, and then to only hundreds."

The collapse was precipitous enough to undermine the old saw that "every great cause begins as a movement, becomes a business, and eventually degenerates into a racket." The movement won no major policy victory, and its remnant had no spoils to divide. "Antiwar Groups Battle for Survival," Politico was reporting by 2010: "Just a few years ago, some groups raised millions of dollars in donations and mobilized legions of supporters…now, UFPJ—which had a full-time, paid staff and a budget of more than $1 million—relies on volunteers working without a headquarters and with less than $100,000 to spend."

Party in the Street's epilogue features a 2013 snapshot of a glum cadre of middle-aged peace activists carrying anti-drone signs outside 1600 Pennsylvania Avenue. The book went to press shortly after President Obama launched America's latest war in the Middle East, against ISIS (a group that rose up in the chaotic and violent power vacuum left by previous wars). Despite Tomahawk missiles raining down on both sides of the Iraq-Syria border, "the mass constituency of the U.S. antiwar movement has gone home," Heaney and Rojas conclude.

True enough: On August 8 the war against ISIS reached its one-year mark. If any of the remaining peace groups staged a rally for the occasion, they didn't muster enough protesters to make it into the mainstream press. Still, the activist website FightBack!News claims that "over 60 people" joined an anniversary protest in Minneapolis, and "several large commercial truck drivers passing by laid on their horns and waved in solidarity."

There's nothing happening here; why that is, is all too clear. The "antiwar movement demobilized in response to Democratic victories," Heaney and Rojas explain. Hordes of activists left the field in the midst of President Bush's Iraq War "surge" and votes by congressional Democrats to fund it via supplemental appropriations. What Party in the Street shows, in sometimes exhausting detail, is a mass "demobilization not in response to a policy victory, but in response to a party victory."

The chart [below], taken from the book, tracks the movement's decline as measured by media coverage during the relevant period. At the protests' Bush-era peak, self-identified Democrats made up 36 to 54 percent of the protesters; after 2009, their presence plummeted to the 20 percent range. "When Democrats stopped turning out, the movement could no longer achieve critical mass."

Beginning in 2009, the Democratic Party had a nearly filibuster-proof majority in the Senate, and the presidency was in the hands of a man whose candidacy caught fire when he promised to "turn the page" on Bush-era "deciderism" and "dumb wars."

"So," Heaney and Rojas ask, "did these antiwar voters get what they bargained for?" Hardly: There was "more continuity than change" in the war policies pursued by the Bush and Obama administrations. As president, Obama stuck to the Iraq withdrawal timetable negotiated by the Bush team, breaking his campaign-trail pledge to have the troops home 20 months earlier. He also ordered an Afghan "surge" on a much larger scale than his predecessor carried out in Iraq; more than 1,500 U.S. troops died in Afghanistan during Obama's first term, nearly three times the toll over Bush's eight years. "The differences between the administrations are subtle," the authors write, adding that "at worst, the Obama administration was somewhat more bellicose" than the GOP alternative would likely have been.

That's unduly charitable, it seems to me. After all, by the time Obama hit the dais in Oslo to accept the Nobel Peace Prize in 2009, he'd already launched more drone strikes than "war president" George W. Bush managed during his two terms. Since then, Obama has racked up more than seven times as many drone strikes as Bush, including the remote-control execution of an American citizen—and has launched two "wars of choice" without a shred of authorization from Congress. In his recent speech defending the Iran deal, President Obama burnished his hawkish bona fides by pointing out that, so far, he'd bombed at least seven countries.

One suspects that this wasn't quite what your earnest neighbor had in mind back in 2008 when he pasted that "Hope" bumper sticker on his Prius. Nor was it the outcome envisioned by the hordes of activists who marched against war during the Bush years. Nonetheless, the peace activists have made their peace with the war-waging president.

"Partisan identification tends to be stronger and longer-lasting than movement identification," Heaney and Rojas explain. After 2006, "Activists were increasingly compelled to choose between their identities. 'Am I a Democrat? Or am I an antiwar activist?' It became difficult to be both."

The authors take pains to deny the charge of "hypocrisy" on the part of partisans who put down their placards when the Blue Team took power. "Our findings suggest an alternative explanation": The activists who left the field before winning any policy victories "continued to dislike the war," but they "trusted Obama to do what was right to remedy the situation," leaving them free to apply their energies to other causes. Many former peace marchers "took direction from party elites to turn their attention to another vital issue: health care."

Here again, the authors are too kind. It's not as if erstwhile peace activists surged back into the anti-war movement once the Affordable Care Act passed in 2010, or even after two Supreme Court decisions put Obamacare out of any plausible legal jeopardy. And given the president's record, there is no remaining basis for the trust they'd initially invested in him.

Alas, political tribalism warps people's perceptions of basic reality, convincing partisans they're entitled to their own facts. That's not new, nor is it limited to one side of the political spectrum. In a 1988 survey, over half of self-identified "strong Democrats" believed inflation had increased under President Reagan; it had actually come down nearly 10 points. Half of the Republicans in a 1996 poll believed Bill Clinton had increased the deficit, though it had dropped steadily during his tenure. Political scientist Adam J. Berinsky puts it starkly: "In the battle between facts and partisanship, partisanship always wins."

What lessons can be learned from the collapse of the post-9/11 anti-war movement? Party in the Street's final chapter offers some "strategies for social movements" at a time of heightened partisanship. They won't do much to cheer would-be reformers of any stripe. "In an era of partisan polarization, social movements risk experiencing severe fluctuations in support concomitant with variations in partisan success," Heaney and Rojas write.

It's a risk that seems nearly unavoidable. Resisting party loyalty is no guarantee that a movement will achieve its goals. The Occupy Wall Street movement of 2011 was so wary of being co-opted by political parties that Occupiers repulsed MoveOn's attempts at solidarity and shouted down Green Party candidate Jill Stein at one encampment. Yet "antipartisanship had the effect of drastically narrowing Occupy's supportive coalition," the authors note.

And though partisanship eventually proved fatal to the anti-war movement, "working with the Democratic party was still most likely the best strategy available." The movement might have benefited from a more aggressive, Tea Party–style approach, Heaney and Rojas suggest, fielding more primary challenges to pro-war Democrats. It could also have sought to establish a funding base independent of Democratic donors and done more to "educate its supporters about the need for continued activism" even after the Democrats took power.

Yet elsewhere, Party in the Street makes clear that it wasn't an "absence of organizational leadership" that led to the movement's collapse; "if anything, the major organizations and coalitions intensified their mobilization efforts in 2007-2008…in the face of declining interest among [the movement's] mass constituency." It's hard to imagine that a wilier strategy could have made movement loyalties stronger than partisan ones. As the authors admit in their first chapter, "The chances that the antiwar movement would have a major influence on war policy in the 2000s appear to have been small from the outset."

Mass opposition to the Vietnam War proved less susceptible to partisanship than the post-9/11 movement—recall the popular chant: "Hey, Hey, LBJ: How Many Kids Did You Kill Today?" Yet Heaney and Rojas cite research to the effect that the stateside Vietnam-era anti-war movement "had only an ambiguous effect on actual U.S. policy in Vietnam" and may even "have helped to prolong the war." Its major policy victory was ending the draft-an impressive achievement, but one that made future wars less politically costly.

Ironically, Barack Obama's first published article, as a Columbia University senior in 1983, explored the dilemma of how activists could motivate people to resist "the relentless, often silent spread of militarism in the country." In a piece entitled "Breaking the War Mentality," he worried that the public's distance from the costs of war made mobilization "a difficult task." For his generation, "military violence has been a vicarious experience…the taste of war—the sounds and chill, the dead bodies" remain "remote and far removed."

Since 9/11, technological advances have further reduced war's apparent cost, enabling what my colleague Ben Friedman calls an era of "one-click wars," where "low upfront cost and ease of delivery encourage whimsical choices uninhibited by debate about value." As president, Barack Obama has perfected that form of warfare and made "breaking the war mentality" more difficult than ever.

If "we are the ones we've been waiting for," we may be waiting a long time.