Benjamin Netanyahu declared war on the Iran nuclear agreement and launched a major lobbying campaign to bury the hated deal crafted by his nemesis, Barack Obama. 

The Prime Minister will be meeting every American politician who comes to Israel during the August congressional recess and working the phones with the rest of them.  He's not only mobilized his government but his political allies, particularly the American Israel Public Affairs Committee (AIPAC).

The number one target of the multi-million-dollar campaign is Sen. Chuck Schumer, the man who claims the title "Shomer Yisrael," guardian of Israel, and wants to be the next Senate Democratic leader.  The challenge facing the Brooklyn Democrat is how to retain both titles.

He's keeping quiet but you can bet he's already had personal phone calls from Obama, Netanyahu and everyone whose ever written a large check for his campaigns and causes.

Although an outspoken critic of Iran and advocate of tough sanctions, he has been careful not to tip his hand, insisting he wants to see the details of the agreement before making any commitment –an uncommon example of statesmanship in an environment in which most Republicans will automatically oppose any agreement that wears President Obama's imprint.

Schumer, now number three in Senate Democratic hierarchy, is the chosen (and presumptive) successor to retiring leader Harry Reid of Nevada. 

Many of his colleagues, not just the undecided, will be watching to see what Schumer does.  He will be the canary in the coalmine who will give the first signals as to whether the deal can survive or will quickly run out of air.

He will be watched for his dual roles as a party and Jewish leader – he has boasted of being Netanyahu's best friend on Capitol Hill. As he goes on the Iran agreement many of his Democratic colleagues are likely to follow, knowing they have the cover of their next leader and a pro-Israel shtarker with nearly 1.8 million Jewish constituents.

Republicans will probably vote unanimously against the agreement, not on the merits but out of spite and politics.  So resolutions of disapproval will easily pass both GOP-controlled chambers and be vetoed.  Obama will then need only one third plus one of the votes in either chamber to sustain his veto. The primary target will be the Senate, where Obama will need 34 of the 46 Democrats, assuming Republicans vote en bloc. 

And that's why Schumer's vote is so critical.  He has called this one of the toughest decisions he's ever had to make. He will face enormous pressure from the White House, from his friend Bibi, from pro-Likud Jewish organizations and from single-issue pro-Israel Jewish political donors.

If Schumer joins the opposition and brings down the President's Iran deal, he can give cover to Democrats who want to vote against it, and he can probably kiss goodbye to his chances of becoming Senate Democratic leader.