President Trump’s decision to authorize a military strike on Iran is a seismic moment that could reshape the future of the Middle East and his presidency.

The administration on Sunday signaled it wants to contain the conflict, underscoring that it does not want an all-out war with Iran but will not accept a world where Tehran has a nuclear weapon.

Whether it can contain the fallout is a different proposition and one that may depend largely on Iran.

Politically, the vast majority of Republicans are sticking with Trump, while many Democrats are expressing outrage over what they see as a lack of strategy, as well as a lack of notification to Congress ahead of the strikes.

The move by Trump is, in some ways, a surprise, as he came to office promising to keep the U.S. out of foreign conflicts. Now, less than six months into his second term, he is on the brink of a larger battle.

Here are five big questions about what comes next.

How does Iran respond?

This is the most important question.

Administration officials on Sunday signaled that they are hopeful Iran will return to the negotiating table, but signs quickly emerged of a more aggressive response from Tehran.

Iranian television reported that Iran’s Parliament had approved a measure to close the Strait of Hormuz, a key shipping route between Iran and Oman. State-run Press TV said a final decision on doing so rested with Iran’s Supreme National Security Council.

Shutting off the waterway could have major implications for global trade, leading to increased oil and gas prices in the U.S. That would bite at Trump, who vowed to bring down prices after years of high inflation under former President Biden in the post-COVID era.

It also risks turning the conflict into a broader war.

Iran could also launch strikes against U.S. military targets, though its abilities to do so have been hampered by more than a week of strikes by Israel, which has allowed U.S. and Israeli planes more security to fly over Iranian skies.

Another widely discussed possibility is that Iran could back terror attacks around the world on U.S. targets.

Of course, there would be serious risks to such actions by Iran.

Just taking steps to move forward with its nuclear program, let alone striking out at the U.S., would lead to negative consequences, U.S. Secretary of State Marco Rubio warned on Sunday.

“Look, at the end of the day, if Iran is committed to becoming a nuclear weapons power, I do think it puts the regime at risk,” he said during an appearance on Fox News’s “Sunday Morning Futures.” “I really do. I think it would be the end of the regime if they tried to do that.”

What do Republicans do?

Before this week, Trump’s Make America Great Again (MAGA) movement looked divided on a strike on Iran.

Trump has long criticized past U.S. wars in Iraq and Afghanistan, and a big part of his draw to many voters was his promise to keep the U.S. out of foreign conflicts.

MAGA voices ranging from Rep. Marjorie Taylor Greene (R-Ga.) to political pundit Tucker Carlson to former Trump strategic adviser Steve Bannon have all cast doubt on getting the U.S. more directly involved in the Iran-Israeli conflict.

In the immediate aftermath of the strikes, Republicans were notably united, with Rep. Thomas Massie (R-Ky.) being a notable exception.

And administration officials with noninterventionist records were taking rhetorical steps to keep the doubters in line. A chief example was Vice President Vance, who said the U.S. was at war with Iran’s nuclear program, not Iran as a country.

Iran may not see things that way, and if Tehran takes steps to hurt the U.S., GOP voices who doubted the wisdom of a strike may get louder.

That will be something the administration watches closely going forward.

Trump, in a Sunday Truth Social post, also touted “great unity” among Republicans following the U.S. strikes and called on the party to focus on getting his tax and spending legislation to his desk. 

What about Democrats?

On the left, Democrats have hit Trump hard over the strike on Iran.

Sen. Bernie Sanders (I-Vt.), speaking at a rally on Saturday night, reacted to unfolding events live, arguing Trump’s action was unconstitutional as a crowd chanted “no more wars.”

Rep. Alexandria Ocasio-Cortez (D-N.Y.) said Trump’s action was an impeachable offense. That was a bold statement in that Democrats largely have avoided impeachment talk with Trump after twice voting to impeach him during his first term. Both of those efforts ultimately ended with Senate acquittals and, finally, with Trump’s reelection last year.

Presidents in both parties have taken limited military strikes without first seeking permission from Congress, but Democrats have also brought up the War Powers Act, saying Trump went too far with the strikes.

At the same time, many Democrats are concerned about Iran’s potential to go nuclear, and the party does not want to be cast as soft on Tehran.

Senate Minority Leader Chuck Schumer (D-N.Y.), a vociferous opponent of Iran, called for his GOP counterpart, Senate Majority Leader John Thune (S.D.), to put the War Powers Act on the floor so senators could vote to authorize Trump’s actions.

Going a step further, Schumer said he would vote for it.

“No president should be allowed to unilaterally march this nation into something as consequential as war with erratic threats and no strategy,” Schumer said in the statement.

“Confronting Iran’s ruthless campaign of terror, nuclear ambitions, and regional aggression demands strength, resolve, and strategic clarity. The danger of wider, longer, and more devastating war has now dramatically increased.”

“We must enforce the War Powers Act, and I’m urging Leader Thune to put it on the Senate floor immediately. I am voting for it and implore all Senators on both sides of the aisle to vote for it,” he said.

Another Democrat further to the center, Sen. John Fetterman of Pennsylvania, reposted Trump’s Truth Social post on the attack and said he fully agreed with it.

In general, the strikes on Iran may further divide Democrats on liberal-centrist and generational lines.

Yet much, again, depends on events. A successful Gulf War by former President George H.W. Bush did not save his presidency in 1992. And the second Gulf War ended disastrously for the Republican Party led by Bush’s son, former President George W. Bush.

Is this a sea-change moment for Trump?

Trump justly had a reputation as a president who is averse to foreign conflicts, given his criticism of wars in Iraq and Afghanistan and his repeated calls that he would keep the U.S. out of such wars.

So how did this Trump end up bombing Iran, becoming the first president to authorize the dropping of some of America’s most lethal nonnuclear bombs?

It’s more likely Trump’s shift is a bit of a one-off based on current world events than a complete change in philosophy.

After Israel’s initial strike on Iran on June 13, the administration distanced itself from the decision. Trump previously had been seeking to get Iran to agree to a nuclear deal, and many reports suggested he was not keen on an aggressive Israeli attack.

But that attack happened, and it went well. Israel had control of Iranian airspace, potentially clearing the way for U.S. B-2 bombers.

Action by Russia was unlikely given its own war with Ukraine something that was not part of the political fabric in Trump’s first term.

Iran’s backers in Hamas and Hezbollah also have been devastated by Israel since Hamas launched its attack on Oct. 7, 2023, an event that has had a number of serious repercussions.

Some U.S. officials on Sunday called for peace, a sign that Trump is not seeking a prolonged conflict.

That could also be a message to his supporters who did not think they were voting for a leader who risked getting the country into a Middle East war. 

At least some of those voters may be asking questions in the days and weeks to come, and what comes next will make a big difference in shaping their views.

Who has Trump’s ear?

Trump’s decision to attack Iran and enter the Israeli-Iran war is a big win for hawkish supporters and allies of the president, most notably Sen. Lindsey Graham (R-S.C.).

It is also, oddly, something that will be cheered by certain Republicans who are more often critics of Trump, such as former national security adviser John Bolton and former Senate GOP Leader Mitch McConnell (Ky.).

It seems clear Trump is listening to the voices of Graham, Rubio and Israeli Prime Minister Benjamin Netanyahu, despite the sometimes-tense relationship between the U.S. and Israeli leaders.

Vance is clearly a part of the president’s inner circle, and it was notable that he, Rubio and Hegseth were at Trump’s side when he announced the strikes on Saturday night.

Trump 2.0 has been notable for having few voices that offer pushback to Trump’s decisions.

It is difficult to see Hegseth pressing Trump to move in a different direction on a national security issue, for example. And Trump twice this week described assessments by Director of National Intelligence Tulsi Gabbard that Iran was not close to developing a nuclear weapon as wrong.

So, who has Trump’s ear? Most of these key people surround Trump and others, like White House chief of staff Susie Wiles.

But Trump is his own decider in chief, and the Iran strikes are a reflection of his own unpredictability.