Several significant events Thursday suggest the Iran sanctions bill’s tipping point has been reached.

Vice President Joe Biden addresses the American-Israel Public Affairs Committee. (Susan Walsh/Associated Press) Vice President Joe Biden addresses the American-Israel Public Affairs Committee. (Susan Walsh/Associated Press)

First, as the co-sponsors on the bill reached 53, a key Democrat — a moderate, not known for outspoken views on Israel — Sen. Michael Bennet (Colo.) signed on. There are now 15 Democratic co-sponsors, despite a virulent White House campaign to bury the bill. Bennet, the first Democrat to join since the main group in December, raises the possibility still more Democrats will defy the White House. It is rare that the Senate gets 54 bipartisan votes on anything, let alone foreign policy, but the news that Iran is still insisting on proceeding with advanced centrifuges and is dragging out the interim agreement may spur others to follow Bennet.

Second, J Street, the most visible anti-sanctions groups which prides itself on blocking and tackling for the president, panicked, sending out an emergency alert today, imploring members to call senators to tell them not to sign onto sanctions legislation. Plainly, Bennet’s decision unnerved the group which unlike every other mainstream Jewish organizations has opposed sanctions, attacked Israel for defending itself against the terrorist flotilla and even embraced the now discredited Goldstone report.

Certainly, J Street has reason to worry. If Bennet is on board then Democratic senators who fancy themselves as pro-Israel — like Maryland’s Barbara Mikulski — will be hard pressed to stick with the White House. (It is especially treacherous for Mikulski since her Maryland Democratic colleague Ben Cardin has signed on.) The long list of co-sponsors, both Democratic and Republican, also heightens pressure on Majority Leader Harry Reid (D-Nev.) to move the bill to the floor.

Interestingly, vulnerable red state Democrats like Mark Pryor (Ark.), Kay Hagan (D-N.C.), and Mary Landrieu (D-La.) quickly signed on, leaving the Democratic stragglers on the ballot like Sen. Jeanne Shaheen (D-N.H.) vulnerable to attack.

Third, the national security group, Foreign Policy Initiative, released a letter with 73 prominent foreign policy gurus urging the Senate and House to act (“given Tehran’s long history of violating its international nuclear obligations — and the lack of any explicit enforcement mechanisms in the Joint Plan of Action’s text — congressional leadership is once again required to set clear standards for enforcing Iranian compliance with the interim nuclear deal.”)

It is also noteworthy that every conceivable Republican presidential aspirant but one in the Senate has become a co-sponsor, Rand Paul (Ky.). That puts him in the small minority of Republicans who have adopted the president’s position and are not seeking to pass sanctions to pressure Iran to give up its nuclear weapons program. This will only deepen suspicions among Zionist Christians that Paul’s charm offensive on Israel is as phony as were President Obama’s 2008 claims to be ready to use military force if needed to keep Iran from going nuclear.

As for potential Democratic candidates, the White House tells us how closely in sync the president is with Vice President Joe Biden, so he must be fully supportive of the anti-sanctions line. And Hillary Clinton? She’s staying undercover, no doubt assessing which way the winds of the Democratic primary are blowing. We know also thanks to former defense secretary Bob Gates’s book that this factor is determinative when it comes to her pre-election foreign policy pronouncements.

The divide then on sanctions is not Democrat vs. Republican, but White House and Tehran vs. the U.S. Congress, the American people (as polls indicate) and U.S. allies. It will be interesting to see which side the remaining 46 senators choose.

Jennifer Rubin writes the Right Turn blog for The Post, offering reported opinion from a conservative perspective.