Barack Obama's chief strategist in his 2008 and 2012 presidential wins, Jim Messina, has explained his approach to politics by quoting the boxer Mike Tyson: "Everybody has a plan until you punch them in the mouth." President Donald Trump last week collectively punched Democrats in the face by ordering a lethal strike against a top Iranian commander, shifting attention from his impeachment and leaving the party's 2020 candidates gasping for a response.

The immediate political payoffs for Trump of the sneak uppercut are clear: The episode knocked out the media's round-the-clock focus on his impending Senate trial on charges of abuse of power and obstruction of Congress, and coverage for days and weeks to come is likely to be consumed with the strike.

Instability with Iran could help the prospects of the Democratic candidate that Trump — and polls — has indicated he has the most reason to fear: former Vice President Joe Biden.

Democrats, meanwhile, have been thrown off-balance in seeking a political response: The target of the operation, Maj. Gen. Qassem Soleimani, the longtime head of the feared Quds Force of Iran's Islamic Revolutionary Guard Corps responsible for hundreds of Americans' deaths, is hardly someone whose loss is mourned by voters. Democratic presidential candidates mostly issued hedged statements condemning Soleimani while questioning the wisdom of the attack, while House Speaker Nancy Pelosi, D-Calif., was reduced to complaining that the strike came "without the consultation of Congress."

But Trump is looking for more than to cut down Democrats; he also wants to shore up support from the broader public so impeachment doesn't doom his presidency. Foreign policy crises have often helped presidents quickly grow their approval ratings and depress partisan criticism — what political scientists refer to as the "rally-round-the-flag" effect. Yet there is little sign that Trump will reap similar rewards, and in fact he may well find that stoking international tensions loses him support at home.

The rally-round-the-flag boost has been well-documented. During and after the October 1962 Cuban Missile Crisis, for instance, President John F. Kennedy's approval rating rose from 61 percent to 74 percent. Amid the 1991 Persian Gulf War, President George H.W. Bush's ratings skyrocketed from 59 percent to 89 percent.

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His son, President George W. Bush, saw a massive improvement in his standing in the tragic and chaotic days following the Sept. 11, 2001, terrorist attacks. Bush's Gallup approval rating of 51 percent on Sept. 10 jumped by 34 percentage points, to 85 percent, by Sept. 15 and eventually peaked at 90 percent — the highest presidential approval rating ever.

But there's at least one major difference between these historical cases and Trump's circumstances: Kennedy and the Bushes started from points of significantly higher public support. Trump's approval ratings have barely changed throughout his presidency, stuck in the low 40s for most of his tenure — only occasionally changing to dip even lower — so there's reason to be skeptical that they will improve much now. Positive events like a soaring stock market, as well as devastating ones like impeachment, have moved the needle little. And both Bushes always scored well in "likability" indexes. Not so much with Trump, whom even some Republicans privately chastise for impolitic behavior while approving his public policy decisions.

Instead, the better historical comparison is likely the one promoted by Hollywood rather than academia: a "Wag the Dog" skepticism. The term stems from a 1997 movie that follows a political consultant (Robert De Niro) and a Hollywood producer (Dustin Hoffman) as they concoct a war in Albania to distract voters from a presidential sex scandal.

And it's not just the stuff of fiction. The plot line unfolded in uncanny real-life fashion when President Bill Clinton in 1998 ordered air strikes against Iraq the night before his own impeachment vote on counts of perjury and obstruction of justice related to the Monica Lewinsky affair.

But even then, Clinton enjoyed advantages Trump doesn't. Despite widespread Republican comparisons between Clinton's actions and the movie plot, Clinton ordered the airstrikes in response to Iraq's refusal to cooperate with U.N. weapons inspectors, with significant public backing. Nearly two years into his second term, Clinton's approval ratings were consistently in the high 50s to high 60s. After Clinton's impeachment proceedings in 1998 and 1999 — ending in a Senate acquittal on both charges — his ratings reached 73 percent, the highest of his presidency.

Trump has nowhere near that level of goodwill. He is the most polarizing president ever, and partisan attitudes about him are baked in on both sides. Democrats are giving Trump absolutely no credit on foreign policy nor the benefit of the doubt on, well, anything.

"This is where having credibility — and having a president who didn't lie about everything — would be really, really helpful," Samantha Power, the former U.S. ambassador to the United Nations, tweeted about the Iran strike.

Moreover, Trump faces the threat that the Soleimani assassination could end up hurting him politically. While Americans don't like Iran, branded a state-sponsor of terrorism and a frequent bad actor in news reports, there's little appetite for full-scale military confrontation following the ravages of the Iraq war. A Gallup poll in July indicated that a mere 18 percent of Americans wanted to "take military action against Iran," while 78 percent wanted to "rely mainly on economic and diplomatic efforts." Republicans were nearly as anti-war as Democrats.

Those attitudes were in play before Trump took office three years ago, but his approach to Iran has exacerbated it. A University of Maryland poll in September indicated that a majority of Americans blame Trump's policies for heightened tensions with Iran.

Meanwhile, reverberations from the Soleimani killing are only beginning. Predictably, Iran's Islamist leaders have vowed revenge, and their counterattacks — in fact, any Middle East violence that spirals from there — could well result in blame for Trump rather than boosterism.

Iran's leaders, no fans of Trump, have previously shown an acute understanding of the timing and rhythm of U.S. politics and presidential popularity. They infamously extended the 1979-81 American hostage crisis, in which U.S. diplomats were held by Iranian jailers, to deflate President Jimmy Carter's re-election hopes.

Trump could face another unfavorable political consequence: Instability with Iran could help the Democratic candidate whom Trump and polls have indicated he has the most reason to fear: former Vice President Joe Biden, who leads his closest rival, Sen. Bernie Sanders, I-Vt., by 10 points in the RealClearPolitics polling average.

Trump’s greatest political triumph in killing Soleimani has been turning the national conversation away from impeachment. Yet that’s likely to prove fleeting.

Biden, past chairman of the Senate Foreign Relations Committee, expands that lead to 48 percent to 14 percent when the question is who is better to handle foreign policy. To be sure, international issues have not been the most important concern for many Democratic primary voters. But a crisis overseas could increase their salience as the early nominating contests get underway Feb. 3.

So far, Trump's greatest political triumph in killing Soleimani has been turning the national conversation away from impeachment. But that's likely to prove fleeting once House Democrats send impeachment articles over to the Senate and a trial begins. And even if the political chatter once again turns to Iran, it will likely be because of Iranian retaliation — with an ugly outcome well making it harder for Trump to land a distractingly effective punch against Democrats.