Since Republicans took control of Congress two months ago, an elaborate tug of war has broken out between Republican lawmakers and President Barack Obama over who calls the shots on major issues for the next two years.
On some fronts, Obama has held his ground, watching near-gleefully as Republicans bungled early attempts to legislate and put their own internal disputes on vivid display. But lawmakers are challenging his authority on foreign policy, threatening to gum up major trade and climate deals while putting up obstacle after obstacle to a nuclear deal with Iran.
Rarely has the separation of powers appeared as muddied as on Tuesday. In the course of a few hours, House Republicans caved to the president on Homeland Security funding and immigration, but also poked him in the eye by giving Israel's prime minister a prime perch before Congress to rail against Obama's efforts to negotiate a nuclear deal with Iran.
The push and pull has laid bare the weaknesses that each party must contend with as they navigate a new political reality.
With his party out of power in the Capitol and his time left in office dwindling, Obama has less clout over Congress than ever before. Increasingly, he's had to resort to veto threats to show he's still the gatekeeper for any laws Republicans want to pass. But despite decisive midterm gains, Republicans have been unable to deliver on campaign promises to rein in the president, illustrating the limits of their power despite their majorities in both the House and Senate.
So who's in charge? It depends, it seems, on the issue.
For months, Republicans had adhered to their plan to use Homeland Security funding to force Obama to swallow a repeal of his executive actions on immigration and deportations. Obama vowed to veto any such bill and Republicans lacked the votes to push it through the Senate. The Republican strategy began falling apart last week when the House leadership couldn't even muster enough support to give themselves more time to fight by extending funding for three weeks.
After passing a weeklong extension with Democratic votes just hours before Friday's deadline, Republican leaders capitulated Tuesday, with little to show for the fight.
"We are pleased that congressional leaders in the House have apparently relented," White House spokesman Josh Earnest said just before the House vote. "They've abandoned the search for political advantage and are instead just trying to move forward to do the right thing."
White House officials said they were holding back from full-on gloating until the bill was passed and signed, and critical Homeland Security funding assured. But the Republican retreat raised serious doubts about whether Congress will be able to use its control of the federal purse strings as leverage against the president.
Yet on the same day, House Speaker John Boehner gaveled in an extraordinary joint session of Congress so that Israeli Prime Minister Benjamin Netanyahu could warn US lawmakers of the perils that await if the US and world powers sign a nuclear deal with Iran. From the same dais where the president delivers his State of the Union address, Netanyahu offered a dramatic take-down of Obama's foreign policy on Iran, winning countless standing ovations from lawmakers as the world watched on live television.
For lawmakers intent on stopping the nuclear deal, Netanyahu's speech - orchestrated by Republicans without the White House's knowledge - was just the beginning.
Senate Majority Leader Mitch McConnell said the Senate next week would start debating legislation granting Congress a vote on any deal reached with Iran - a notion Obama has already rejected. McConnell said he was worried about the Obama administration's "seeming determination to pursue a deal on its own, without the input of the people's elected representatives."
Senators are also pursuing new sanctions on Iran, despite the White House's insistence that doing so now would scuttle the talks and make it more likely Iran will obtain a nuclear weapon. But Senate Democratic leader Harry Reid urged everyone to "take a deep breath" and consider whether new Iran legislation would actually help Israel or merely serve to "score cheap political points."
On domestic matters, too, Obama and Republicans are tussling over whether the president's authority should reign supreme. Republicans are looking to the Supreme Court to derail a key component of Obama's health care law, and hoping the courts will stop Obama where they could not on immigration, too. Last month, Republicans successfully passed a bill forcing Obama to approve the Keystone XL pipeline, but Obama promptly vetoed it, although Republicans are attempting this week to override his veto.
In a bit of irony, Obama also faces Democratic resistance to his flexing of presidential power. Democrats have opposed Obama's calls for the authority to negotiate trade deals with Europe and Asia that Congress couldn't modify. And while Republicans have sought to authorise Obama to intensify the US military campaign against the Islamic State group, many Democrats are pushing for a more restrained war powers resolution.