Julian Zelizer, a CNN political analyst, is a professor of history and public affairs at Princeton University and author of the forthcoming book, "Burning Down the House: Newt Gingrich, the Fall of a Speaker, and the Rise of the New Republican Party." Follow him on Twitter: @julianzelizer . The views expressed in this commentary are his own. View more opinion at CNN.

As Iran decides how it will respond to the US, the country's security body has threatened to avenge Soleimani's death. Meanwhile, President Donald Trump stirred the international waters even further on Saturday by tweeting a "WARNING that if Iran strikes any Americans, or American assets, we have targeted 52 Iranian sites (representing the 52 American hostages taken by Iran many years ago), some at a very high level & important to Iran & Iranian culture, and those targets, and Iran itself, WILL BE HIT VERY FAST AND VERY HARD."

With bated breath, Americans are waiting to see how this crisis unfolds. Some fear that we might be on the verge of a hot war. Online searches about the draft and World War III have surged, and the website for the Selective Service crashed.

Democrats are trying to figure how to respond to the Trump administration's failure to consult with Congress in advance, and have questioned whether the President has a clear strategy and rationale behind taking this step. Further, Democrats are considering what tensions with Iran will do to the election campaign and how it should impact the deliberations over impeachment.

The right answer is that the conflict with Iran should not change the Democrats' overall strategy regarding Trump or the questions they have about his fitness for office.

The Democratic candidates have already started to offer their thoughts on what should be done. Sen. Bernie Sanders has called for a much broader reconsideration of foreign policy, voicing his support for withdrawing forces from the entire region and introducing legislation to block funding for a war with Iran. Sen. Elizabeth Warren has expressed a similar critique of Middle East policy and called on the nation to reconsider its overall approach in the region.

The moderates like former Vice President Joe Biden and Sen. Amy Klobuchar have tried to balance discussions of the very real threat from the Iranian regime with tough questions about how the President has handled the situation -- ordering a provocative killing without fundamentally changing the regime. The President "tossed a stick of dynamite into a tinderbox," Biden said. Pete Buttigieg spoke on CNN's "State of the Union" about coming from a generation that has seen a series of wars, all of which promised to be quick, but turned into quagmires.

But while candidates certainly must discuss their positions on Iran, voters, most likely, will remain primarily concerned about other issues. The best strategy is for the candidates to remain focused on the policy issues that matter most to voters, such as improving their economic security and saving kids from gun violence. These domestic issues will continue to loom largest in voters' minds, especially because the US no longer has a draft that impacts masses of the country (Congress abandoned the system in 1973).

History has shown this to be the case. Even one of the biggest foreign policy successes of the post-Cold War period, Operation Desert Storm in 1991, carried out under the watch of President George H.W. Bush, didn't prevent Arkansas Gov. Bill Clinton from defeating the incumbent in the 1992 election. In our short-attention span era, this dynamic will be more pertinent than ever.

At an even broader level, the international crisis does not change the basic critique that Democrats have been making about why Trump can't be trusted with the responsibilities of this office.

The articles of impeachment, for example, revolve around Trump's willingness to use foreign policy for personal ends. Democrats have argued that his withholding of aid on the condition he be granted an investigation into an electoral opponent has undermined his credibility in irreparable ways. Because his alleged actions in Ukraine were such an egregious violation of presidential power, they instantly put a number of big questions about his recent decisions on the table.

If the President has been willing to withhold foreign military assistance to secure campaign help, how could Americans trust him when he launched a military strike against another country? Was Solemani's killing done in the national interest or in Trump's self-interest? Did the President create serious instability for his own needs, possibly even in an effort to divert public attention from the impeachment.

The public also cannot automatically accept what Trump has to say about Iran as true. After all, there is now a long list of false, misleading and inaccurate claims that Trump has made since his inauguration in January 2017 -- on issues of little importance (the crowd size at his inauguration) and with large consequences (conspiracy theories about Ukraine meddling in the 2016 election that echo Russian propaganda).

Trump's willingness to dispense with the truth poses a huge national security risk. In this fraught moment, there is no reason that voters, who might well determine whether deadly actions for our troops are taken, should automatically take the President's statements about Soleimani posing an "imminent threat" to be true. The credibility gap is immense and undermines the stability of support for the administration's policy.

The President keeps adding fuel to the fire. His tweets that threaten international war crimes against Iran, namely intentionally striking cultural targets, in retaliation for any attacks suggest that Trump has not really learned any lessons about the limits of presidential power. When he is in a tough moment, his instinct is to flex power even more aggressively and in ways that can fundamentally violate international rules and domestic law.

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With Iran, the same concerns about Trump's service as President remain as relevant as ever, and perhaps are even aggravated. Can the President be trusted to handle the role of commander-in-chief?

Democrats have been saying no over and over again. And as people look at the events of the last few days and wonder why the President generated this level of turmoil, many will only see further evidence that the Democrats have been right all along.