The call from the White House was not unexpected. Back in New Jersey for the August recess, Sen. Robert Menendez answered the phone Thursday evening, fully expecting to learn final details of President Obama's plan for attacking Syria.
The Democratic senator, a social liberal with foreign policy views that border on the hawkish, is in his rookie season as chairman of the Foreign Relations Committee. The Syria chemical-weapons crisis would mark Menendez's first moment front-and-center on the international stage as leader of the critical Senate panel.
It was to be a chance for the backroom brawler from the city streets of North Jersey to finally step out of the shadow of his predecessors, John Kerry (now secretary of state) and Joe Biden (now vice president) -- and to prove to his critics he deserved his coveted spot.
That Thursday phone call was not unexpected. But it did offer a surprise. A huge surprise. Instead of hearing strike details, Menendez listened as the president explained he was thinking of altering course and holding off on an attack so he could secure congressional approval for military action.
Never a fan of Obama or his laid-back style, which the administration described during the build-up to effort to depose Libyan strongman Moammar Gadhafi as "leading from behind," Menendez was now on the verge of becoming the unlikely go-to guy for a White House quickly bleeding support and credibility.
Less than two days later, Obama went to the Rose Garden to make official his plan to go to Capitol Hill. With that, the president put Menendez -- a man he doesn't like -- in charge of what could be the most critical foreign-policy initiative of his fledgling second term.
"When you're president, you don't always get to choose the legislator you need on a particular issue," said Princeton University public affairs professor Julian Zelizer, an expert on presidential leadership.
But, Zelizer acknowledged, Obama's decision to deputize Menendez on such a critical issue is "risky."
"The whole thing (Syria attack question) is risky at this point and, on top of it, to have a Democratic who's shaky on you can make you nervous," Zelizer said. "Obama is going to be a little bit nervous. This is someone he doesn't fully trust."
The curtain will rise on this new Menendez-Obama alliance when the senator gavels his committee to order this afternoon. Among the first witnesses expected to be called are Kerry, Defense Secretary Chuck Hagel and Gen. Martin Dempsey, chairman of the Joint Chiefs of Staff.
Menendez declined be interviewed Monday, saying through a spokesman he was busy planning.
The chairman has kept a very low profile since the president's speech on Saturday, canceling his only public event and issuing only general written statements.
Menendez, in a release issued after Obama's announcement, repeated his belief that Bashar al-Assad and his government must be punished because of evidence showing it assaulted its own people last month with chemical agents.
"It is my view that the use of military force in Syria is justified and necessary given the Assad regime's reprehensible use of chemical weapons and gross violation of international law," Menendez said, echoing Obama's own comments. "I look forward to sharing these views with my colleagues in the days ahead as the Senate Foreign Relations Committee convenes to take up this vital national security issue."
What has been left unsaid is the Obama-Menendez history that looms large for two former Senate colleagues, both well-spoken lawyers and former state lawmakers whose careers in Washington were born in the tough, old-school political incubators of Chicago and Jersey City.
"This is an extraordinary moment," one Menendez intimate told ABC News. "It's a moment of sweet -- not revenge because that would be too strong. But it's a moment that's sweet."
The mutual disdain between Obama and Menendez goes back to the earliest days of the 2008 presidential election.
Menendez was an early and vocal supporter of Hillary Clinton's bid for the Democratic nomination and even after she conceded defeat to Obama, Menendez still declined to play along as a loyal party soldier. In return, the Obama campaign marginalized Menendez, despite his huge base of support in the vote-rich Hispanic community.
Grudgingly, Obama's team did offer Menendez a speaking slot at that year's Democratic National Convention in Denver. It would have been the only opportunity for a New Jerseyan to address the convention and observers figured it would mark the burying of the political hatchet between the men.
But Menendez was to speak during the low-viewership hours before prime time and Menendez, incredibly, snubbed Obama. First, he turned down the offer and did not speak and then his intimates made sure key reporters were aware of what had happened.
There was little thaw between the two men after Obama was sworn in, as Menendez made clear he would resist administration efforts to loosen the 50-year-old embargo against Cuba.
And when questions were raised a few months ago about Menendez's friendship with a Florida doctor and political donor under FBI investigation, some around the senator wondered whether some in the administration were getting back at Menendez.
But just as Obama spent the last five years learning how hard it is to govern, Menendez spent the time traveling the country, consolidating power, accruing political credit and accumulating chits. He led the Democratic Senatorial Campaign Committee for a cycle and threw himself into helping re-elect other Democrats who were sure to owe him down the road.
"He's an institutional guy," the Menendez source said. "He's not an outsider. He knows how to work from the inside. It's the same way he did it when he became chairman of the Democratic conference in the House. If there's a coalition to be put together, Bob can do it."
That's why, the person explained, Obama is willing to turn to Menendez at such a critical juncture.
"This is a guy who can count heads and run the committee and, for his own independent reasons, has come to the same position as the president on Syria," he said.
Zelizer said Menendez also has the chance right now to use the Syria crisis and the weight of the White House to push back against critics, like The New York Times editorial board, who suggested the senator was "never a distinguished choice" to lead the Foreign Relations Committee.
"This is a big-opportunity, high-profile moment for him," Zelizer said. "Electoral interests and party interests are big in Washington, and those could easily overcome any kind of personal animosity these two men have for each other."