Between Thursday and Friday, five of the remaining 10 undecided Democrats announced their positions. Four of them, New Jersey’s Corey Booker, Virginia’s Mark Warner, North Dakota’s Heidi Heitkamp, and Colorado’s Michael Bennet, all announced their intention to vote in favor of the agreement.

But Maryland Senator Ben Cardin came down on the opposite side of the issue and this was embraced as a significant victory for the opposition, in light of his position as the ranking Democrat on the Senate Foreign Relations Committee. He is only the third Senate Democrat to break with President Obama on this issue, though all three of them hold especially high rank. New York’s Charles Schumer is poised to become the new party leader, and New Jersey’s Robert Menendez formerly chaired the Foreign Relations Committee.

According to Roll Call, this has led Republican Senator and current Foreign Relations Committee Chairman Bob Corker to claim that the Democrats who are opposed to the deal are the ones who are most informed about its details and context, having spent more time than all others studying as part of their foreign policy roles.

It is not clear that more information would have changed their positions on the deal, but many of the Democrats who have come out in support of it have also expressed serious reservations, acknowledging that the deal is “imperfect” or “deeply flawed.” In some cases, their support comes as a surprise to some analysts.

For instance, Senator Booker was viewed as a possible vote against the deal in light of his longstanding relationship with the Jewish community in his state. His newly declared support is made more surprising by the content of his statement, which the Jewish Press quoted as referring to a “deeply flawed deal.”

Senator Bennet’s skepticism about the deal apparently goes even further, as the Denver Post points out that he is working together with Senator Cardin to introduce legislation to strengthen and supplement the agreement, despite their opposite positions on the resolution of disapproval.

This sort of agreement-in-opposition may suggest that the two do not have fundamentally different views of the agreement, but are pursuing somewhat different strategies about how to deal with it in light of its imminent passage. Mikulski’s announcement on Wednesday all but guaranteed that President Obama’s veto of the forthcoming resolution will be sustained. The four new votes presumably express party loyalty but have no real impact on the material outcome of the vote, which is due by September 17.

However, the additional support has moved the president to within two votes of having enough support to potentially prevent the resolution of disapproval from even reaching his desk. If the number of supporters of the deal reaches 41, they will be able to employ the rules of the filibuster to prevent the resolution from going to a vote, thus stripping Congress of an opportunity to send a clear message that the government is divided on the issue of implementing the Iran nuclear agreement.

On Thursday, Forward claimed that Democratic support was unlikely to go this far, especially given the size and political clout of the Jewish constituencies for the remaining undecided senators. Furthermore, these individuals may not wish to suffer the political consequences of blocking the expression of popular opposition for the deal, even if they personally support it.

Most public polls in recent weeks have shown that a majority of Americans do not think the nuclear deal is sufficiently strong and believe that Congress should vote against it.

Forward’s claims were printed before decisions were announced by either Bennet or Cardin, and it is unclear how their contrary positions have affected the prospects for filibuster. But what is clear is that the deal is almost certain to go into effect at the end of this fight, leaving its staunch opponents to pursue other measures to alleviate their concerns that it will fail to prevent Iran from obtaining a nuclear weapon while also providing the country with money to spend on financing terrorism.

The Bennet-Cardin bill strives to address these concerns, as by formally declaring that all options remain on the table, including the military option, if there is any evidence of Iran cheating on the deal. It also emphasizes that US sanctions will not be fully removed from Iran until the latter has made a clear commitment to upholding its obligations under the deal.

Furthermore, the bill would require that the president routinely report to Congress on how Iran is spending the assets it regains access to under the deal, as well as setting the stage for the speedy re-imposition of sanctions in the event that Iran is found to be behind the financing or planning of terrorist plots targeting the West.