Updated 6:23 p.m. | The path to block disapproval of the Iran deal from ever getting out of the Senate appeared to be at hand Tuesday, just after Minority Leader Harry Reid made the case for why doing that should be perfectly acceptable.  

But there’s an element of kabuki in all of this, because the votes are already there to sustain a veto by President Barack Obama. Debate on the Senate floor is expected to take place throughout the week, with intensity picking up after the first caucus lunches of the September work period, scheduled for Wednesday.  

On Tuesday, West Virginia Sen. Joe Manchin III became the fourth Democrat to announce opposition to the international agreement with Iran regarding nuclear development. It came on the day Senate debate is set to begin — and with activity around Washington for and against the deal, as lawmakers return from August recess.  

“For me, this deal had to be about more than preventing Iran from acquiring a nuclear weapon for the next 10-15 years. For me, this deal had to address Iran’s terrorist actions. Without doing so would reward Iran’s 36 years of deplorable behavior and do nothing to prevent its destructive activities,” Manchin said in a statement.  

But Manchin and the other Democratic opponents were rolling against the tide.  

As of late morning Tuesday, there was just one undecided Democrat left in play: Maria Cantwell of Washington. Sens. Gary Peters, D-Mich., Ron Wyden, D-Ore., and Richard Blumenthal, D-Conn., all announced their support for the deal Tuesday, in statements just before noon.  

Cantwell told reporters later Tuesday that she too would support the deal, making her the 42nd Democratic senator to do so.  

“Rejecting this agreement is fraught with unacceptable risk. Our formal negotiation partners and allies have signaled clearly that they are not coming back to the table — a point confirmed in my conversations and meetings. There is no better deal available now. The present sanctions will soon become unenforceable, producing an economic windfall for Iran whether or not the United States accepts the agreement,” Blumethal said in his statment. “The United States, instead of Iran, would be isolated. Iran’s nuclear program would be unconstrained. Rejection would fracture our unified efforts with allies and greatly weaken international pressure on Iran and American leadership, especially if economic sanctions are needed.”  

Reid, speaking Tuesday morning to the Carnegie Endowment For International Peace, affirmed what became clear last week when retiring Democratic Sen. Barbara A. Mikulski of Maryland announced her support: The Iran deal will hold.  

“The Senate, of course, has an important oversight role to play. When we voted nearly unanimously for the Iran Review Act, we voted to give the Senate that role. We voted to consider three possible outcomes: no action at all, a resolution of approval, or a resolution of disapproval,” the Nevada Democrat said. “It is absurd to argue — as some are doing now — that by voting for a process with three possible and very different outcomes, senators somehow obligated themselves to vote to advance a specific outcome. They did no such thing.”  

The legislation that allowed for the review period for the agreement, which passed the Senate 98-1 en route to a presidential signature, contains no provisions creating an expedited process working around the Senate’s debate rules.  

“There is no precedent in recent history for an issue of this magnitude getting consideration in the Senate without having to secure 60 votes. This is not about how any one leader manages the floor — this is a precedent stretching back decades,” Reid said.  

Reid said it was entirely consistent for the Senate to opt to take no action advancing legislation, which now seems likely.  

In a Tuesday morning statement, Sen. Tim Kaine, one of the authors of the review measure, backed Reid’s point about the measure needing 60 votes to advance. However, it was not clear that all supporters would oppose limiting debate.  

“I was the co-author of the Iran Nuclear Agreement Review Act under which Congress is considering the international agreement to prohibit Iran from obtaining nuclear weapons. The bipartisan bill — to give Congress a deliberate and constructive review of the final nuclear agreement with Iran — was drafted so that 60 votes would be required in the Senate to pass either a motion of approval or a motion of disapproval,” the Virginia Democrat said.  

Republicans contend that Democrats should not prevent an up-or-down vote on the disapproval resolution.  

Majority Leader Mitch McConnell, R-Ky., said on the floor that senators should be in the chamber Wednesday afternoon.  

“I expect that every senator who voted for that measure is now entitled to an up or down vote — not a filibuster or artificial limits on passage, but an important vote — on this resolution,” he said. “Along with the Americans we were sent there to represent, countries, businesses, and proliferation networks seeking to expand ties with Iran stand to have simple question answered: Does the Senate disapprove of this deal with Iran?”  

And Arkansas GOP Sen. Tom Cotton, the lone senator to oppose the review legislation, echoed that sentiment.  

“[N]ow Senator Reid is threatening to filibuster the resolution and deny the American people — through their representatives in the legislative branch — an opportunity to even have their voices heard. This is unacceptable,” Cotton said in a statement. “On a matter so critical to national security — one which people on both sides of the debate acknowledge will have generational impacts — blocking the Senate from voting on a resolution would be an insult to our constitutional system and a black mark on the institution.”