WASHINGTON -- Sen. Al Franken moved from "leaning" to backing the Iran deal earlier this week to "supporting" it in an op-ed published on CNN.com Thursday.

"This agreement is, in my opinion, the most effective realistic way to prevent Iran from getting a nuclear weapon anytime in the next 15 years," he wrote, "there's no doubt in my mind that this deal represents a significant step forward for our national security."

When asked about the agreement in an interview in July, Franken did not sound indecisive.

"From what I've seen so far, this appears to be the best option from preventing Iran from getting a nuclear weapon," Franken said last month. "I haven't heard of another option. I have asked everyone what happens if we strike and what does that look like and it's not very pretty."

The junior senator did not attend the speech delivered by Israeli Prime Minister Benjamin Netanyahu in March to Congress. In the speech, Netanyahu warned members of Congress against supporting the deal, which was then tentative.

The White House is amid a major lobbying effort peddling the deal to Democratic members of Congress -- scattered across the country on August recess. Sen. Amy Klobuchar announced support Monday. 

Democratic Reps. Betty McCollum, Keith Ellison and Tim Walz all say they support the deal. Republican Reps. Tom Emmer, John Kline and Erik Paulsen have signaled they will vote against it next month when Congress returns to Washington.

Undecided are Democratic Reps. Collin Peterson and Rick Nolan.