Ali Gharib reviewed the provisions of the Corker-Cardin “compromise” bill on Iran last week:

As the details emerged, the administration said that it wasn’t “particularly thrilled“ with the Senate compromise, but that it could live with the results. And indeed the deal poses some risks. For example, the bill retains a provision that bars Obama from waiving sanctions during a congressional review period, though that period was reduced from 60 to a maximum of 52 days. Proponents of the bill have insisted that the waiver ban won’t affect ongoing negotiations, but it almost certainly will because it will delay the kind of early sanctions relief that Tehran has made its top priority. Ironically, such a delay may actually strengthen Iran’s hand in the upcoming talks, as U.S. negotiators may now be expected by both Tehran and Washington’s P5+1 partners to give something in return.

The good news is that the modified bill is an improvement over the earlier Corker-Menendez bill. Some of the worst provisions, including the provision tying certification that Iran isn’t sponsoring terrorism to sanctions relief, have been removed, and the review period has been shortened. These represent setbacks for the would-be saboteurs, which is why Iran hawks are not very pleased with it and why Obama has said he would sign it in its current form.

But there’s a good reason why the administration isn’t “particularly thrilled” with the bill. While it is better than the earlier version of the bill, it is nonetheless an unnecessary piece of legislation, and it is still possible that the bill could be amended to include deal-breaking conditions such as Rubio’s ridiculous proposal that Iran be required to recognize Israel. Even without any harmful amendments, the bill is still creating new and unwelcome obstacles to sanctions relief, and that alone could make it harder to finalize a deal. Because the timing of sanctions relief remains one of the more difficult and important parts of the final negotiations, as Gharib says, the possibility that Congress will cause an additional delay before sanctions are lifted weakens the U.S. negotiating position. Even if the “compromise” bill is better than the original version, it is still unwarranted meddling that could make the negotiations more difficult to conclude successfully by creating doubt that the U.S. intends to fulfill its part of the deal in a timely fashion.

The main virtue of the new bill is that the opponents of a deal will still need to have enough votes in both chambers to override a veto in order to disapprove of any deal. Gharib explains:

For one, House Minority Leader Nancy Pelosi has vowed to keep her caucus together to defend a final agreement, and she only needs to keep 145 of her Democrats on board—the one-third-plus-one threshold that’s necessary, under the bill as approved by the Foreign Relations Committee, to sustain a presidential veto of any deal-killing measure. In the Senate, that looks to be a taller order, but keeping 34 Democrats in check could still work.

And that, ladies and gentlemen, is the crowning achievement of this compromise for the Obama administration: it has positioned itself to keep Congress from scuttling an Iran deal so long as it can keep one-third-plus-one votes in either chamber in line.

The saboteurs haven’t been beaten yet, but they are now less likely to be able to wreck a final deal with Iran than they were earlier this year. Congressional meddling in these talks still isn’t helpful, but now it may not be so harmful that it sabotages the negotiations.