Just before the official start of debate in Congress about the Iran nuclear deal, a group of Democrats announced their support for the agreement, raising the possibility that a GOP resolution to block the Iran agreement might not make it past a filibuster in the U.S. Senate.

"No issue that I have faced as a Member of Congress has been more consequential than the one before us now," said Sen. Gary Peters (D-MI), who joined other Democrats in a flurry of announcements supporting the Iran deal.

By the end of the day on Tuesday, 42 Democrats had announced their support for the Iran nuclear agreement, and Democrats were optimistic they could prevent Republicans from sending the disapproval resolution to the President, avoiding a veto showdown.

"While this is not the agreement I would have accepted at the negotiating table, it is better than no deal at all," said Sen. Richard Blumenthal (D-CT), who was seen as a possible 'No' vote on the agreement.

The orchestrated announcements by Peters, Blumenthal and Sen. Ron Wyden (D-OR) came shortly after Senate Democratic Leader Harry Reid gave a speech here in Washington, arguing diplomacy is better than military action against Iran right now.

"I am gratified to say: this agreement with Iran will stand," Reid said.

Not every vote swung in favor of the agreement, as Sen. Joe Manchin (D-WV) - who had been seen as a likely supporter - said he would vote against the plan.

"For me, this deal had to be about more than preventing Iran from acquiring a nuclear weapon for the next 10-15 years," Manchin said in a written statement.

But Manchin's vote was soon old news, as the Democratic side added its way up to 41 votes in the Senate for the agreement, which would give President Obama a big foreign policy victory on Iran and its nuclear ambitions.

Votes are expected on the GOP legislation dealing with the Iran agreement by the end of the week in the House, and maybe in the Senate as well.

As for why this is not being dealt with like a treaty, I offer this from past research this summer: