As President Obama attempts to make good on his threats to punish Syrian officials for crossing a "red line" by allegedly using deadly chemical weapons, he's being buffeted by political crosscurrents.
Some arise from the structure of U.S. democracy itself, and the balance of powers between the branches. Others emerge from the nation's particular state of mind after more than a decade of war in Afghanistan and Iraq.
Here are six points to keep in mind as Obama considers how best to demonstrate American resolve to Syrian President Bashar Assad.
Warring over war powers Obama faces pushback from Congress, which defends its prerogative to declare war, just as other modern presidents have when they've sought to exercise their commander-in-chief role.
In the post-Vietnam era, before presidents have committed the U.S. military to hostilities, lawmakers have frequently demanded usually without success that presidents first seek congressional approval. At the very least, they asked presidents to abide by the War Powers Act and seek congressional approval after U.S. forces enter hostilities.
Often, a president hears the greatest calls for congressional consultation and approval from members of the opposing party. Reactions of the House leadership to private briefings from Obama and other White House officials, for instance, cleave along such lines. Speaker John Boehner, R-Ohio, has indicated publicly that he isn't yet convinced by Obama's arguments. It appears Rep. Nancy Pelosi, D-Calif., is, however.
One of the few things congressional Republicans and Democrats seem to agree on these days, however, is that they don't want Congress to be an afterthought. Two letters to Obama, one from House Republican Rep. Scott Rigell with mostly GOP signatures, the other from California Democrat Rep. Barbara Lee signed by Democrats, raise similar points.
They call on Obama to provide greater details about the intelligence and possible military strikes and to seek congressional authorization beforehand. An NBC poll indicates that about 80 percent of the public agrees with those lawmakers. For Obama, a congressional vote could be treacherous if it resulted in a vote like that in the British Parliament against military action.
Tea Party/libertarians The debate over the constitutional powers of the president versus Congress when it comes to military action has only intensified as Tea Party and libertarian lawmakers have joined congressional Republican ranks. So Obama is dealing with an even more conservative Republican Party on these issues.
These lawmakers tend toward strict constructionist readings of the Constitution. One of their most common allegations against Obama is that his actions have been unconstitutional across a range of policies.
Sen. Rand Paul, R-Ky., is perhaps the best-known of those lawmakers. "The Constitution is very explicit on this: When you go to war, Congress must authorize this," Paul said on Fox News Live Friday.
They also tend to be suspicious of U.S. involvement abroad, making them heirs to the isolationists of the past century.
Liberals -- As with Tea Party and libertarian Republicans, a noninterventionist strain exists among Congress' liberal Democrats, and Obama is bumping up against that.
"We are not the world's policeman," Rep. Alan Grayson, D-Fla., said in a tweet Thursday. On MSNBC Friday, following Secretary of State John Kerry's presentation of the administration's case against the Syrian government, Grayson said he continued to oppose military action against the Assad regime.
"We still haven't heard anything that would explain why there's a vital U.S. national security interest in attacking Syria," he said.
The 2014 election The midterm campaign has already begun. And while the second-term Obama doesn't have to worry about getting re-elected, plenty of others in Washington do.
That means lawmakers will want to have as much daylight between themselves and Obama as possible on Syria if U.S. military strikes result in bad, unintended consequences.
A deeply divided public suggests military action is likely to be unpopular with large swaths of voters. A new NBC poll indicates that while 50 percent would support U.S. military strikes against Syrian military targets, 44 percent are opposed.
No Democrat needs to be reminded that one reason Hillary Clinton failed to win her party's 2008 presidential nomination was her vote to authorize the Iraq War. Obama campaigned on his opposition to that war, which started while he was still an Illinois state legislator, all the way to the White House.
Meanwhile, being on the same side of an issue as Obama is typically not the recipe for a Republican lawmaker to win a GOP primary.
Iraq flashbacks The Obama administration is aware it's paying for the failure of the George W. Bush administration to find weapons of mass destruction in Iraq.
"Our intelligence community has carefully reviewed and re-reviewed information regarding this attack," Kerry said Friday. "And I will tell you it has done so more than mindful of the Iraq experience. We will not repeat that moment."
Kerry has a long history as a critic of U.S. military misadventures, first as a young Navy veteran during Vietnam, then as a senator who lambasted George W. Bush's prosecution of the Iraq and Afghanistan wars. So he's a careful messenger on the course the administration is taking.
But the reactions of lawmakers reflect the post-Iraq distrust and cynicism of many of their constituents on the Syria issue. Kerry's reassurances may be no match for those negative sentiments.
Political payback Obama catapulted to the U.S. Senate largely because of how well he campaigned on his opposition to the Iraq War. In 2007, Obama criticized Bush's threats to unilaterally strike Iran to stop its quest for a nuclear bomb.
Now that he's president, the shoe's on the other foot, and some conservatives are pointing to what looks like hypocrisy on Obama's part.
This is definitely getting in the way of Republican lawmakers' willingness to give Obama the benefit of the doubt on Syria.