The American military strike in Baghdad that killed the Iranian general Qassim Suleimani rippled instantly through the Democratic presidential primary on Friday, forcing national security issues to the fore of a race dominated so far by domestic policy and perhaps stirring debates among Democrats over matters of war and peace.
The party’s presidential candidates reacted to the strike with a measure of unity, at least on the surface level, with expressions of concern about what they called the Trump administration’s penchant for reckless action and the possibility of all-out war. While several deplored Suleimani’s role in directing violence against Americans, the Democrats expressed anxiety rather than jubilation over the circumstances of his demise.
Former Vice President Joseph R. Biden Jr. said President Trump had “tossed a stick of dynamite into a tinderbox,” while Senator Bernie Sanders of Vermont warned that the attack “brings us closer to another disastrous war in the Middle East.”
“Our priority must be to avoid another costly war,” Senator Elizabeth Warren of Massachusetts wrote on Twitter.
But there were also distinctions in how the leading Democrats responded, pointing the way toward a larger debate in the party about foreign wars and the American presence in the Middle East. Mr. Sanders, for instance, notably used the word “assassination” to describe the killing of the Iranian commander — a term with serious legal and diplomatic implications — and pointed out that he had opposed the 2002 resolution authorizing war in Iraq, leaving unsaid that Mr. Biden had supported it.
The degree to which military matters come to dominate the primary, in the remaining month before the Iowa caucuses, will likely depend on events in the Middle East, and how severe and visible any ensuing clash with Iran turns out to be. Foreign affairs have played a strictly limited role so far in the Democratic race. There have been major debate-stage duels over health care, taxation, immigration, criminal justice and gun control, but only glancing disagreements about the role of the United States abroad and the proper way to resolve American military engagements in the Middle East and Central Asia.
In 2020, the possibility of a new and protracted conflict abroad could well reshape the general election, even beyond the Democratic race. Mr. Trump ran for president on a pledge to pull back the United States from foreign wars, drawing support from unconventional quarters for a Republican because of the perception that he would pursue an “America First” policy of relative isolationism and national self-interest.
But Mr. Trump had already drawn criticism from his Democratic rivals, and even within his own party, for presiding over a chaotic pullback from Syria, and the eruption of large-scale violence in Iran and Iraq could profoundly complicate his aim to seek a second term on a message of peace and prosperity.
In the Democratic primary, foreign policy experience has largely been regarded as an asset of Mr. Biden, given his global stature as a former vice president and his background as chairman of the foreign relations committee in the Senate. He has made restoring American alliances around the world a central theme of his campaign and criticized Mr. Trump for turning the United States into a punch line at gatherings of global leaders.
An intensifying debate over foreign policy could have the effect of both spotlighting Mr. Biden’s extensive résumé and also subjecting his track record in the region to new scrutiny. There have been signs in recent days that several of the leading Democratic candidates were angling for a foreign policy debate with Mr. Biden, even before the outbreak of violence in Iraq and the Suleimani killing came to dominate the news.
Mr. Sanders has campaigned consistently on his antiwar record, and he has repeatedly highlighted Mr. Biden’s past support for the Iraq war, warning Democrats that Mr. Trump would use that record against the former vice president in a general election. On Friday morning, an aide to Mr. Sanders posted images on Twitter showing the progressive lawmaker speaking out against war in Iraq in 1991, 1998, 2002 and 2014.
Pete Buttigieg, the former mayor of South Bend, Ind., has attempted to counter questions about his own relative inexperience by pointing to Mr. Biden’s stances on Iraq, as an example of how experience was not always an asset in campaigning or governing.
“He supported the worst foreign policy decision made by the United States in my lifetime, which was the decision to invade Iraq,” Mr. Buttigieg said in an Iowa television interview.
Ms. Warren, too, has indicated in the past that she takes a skeptical view of American military involvement in the Middle East, and declared in one of the fall debates that the United States should remove its combat troops from the region. That stance could become a dividing line in the primary, separating progressives like her and Mr. Sanders from Mr. Biden and others.
For now, much of the Democratic field was proceeding with — and recommending — caution. Former Mayor Michael R. Bloomberg of New York released a statement questioning whether the president had fully considered “the grave risks involved,” while Senator Amy Klobuchar of Minnesota called on the administration to consult with Congress about a “strategy for preventing a wider conflict.”
There is some precedent for events overseas reshaping American primary elections, usually to the benefit of a candidate regarded as a figure of experience. In December 2003, the capture of Saddam Hussein in Iraq formed a backdrop for the final phase of a Democratic presidential primary that yielded the quick nomination of John F. Kerry, a Vietnam veteran who served on the Senate Foreign Relations Committee.
Four years later, the assassination of Benazir Bhutto in Pakistan, in December 2007, pushed national security to the center of an unsettled Republican primary that ended with the nomination of John S. McCain, the war hero whose campaign focused overwhelmingly on the wars in Iraq and Afghanistan.