WASHINGTON (AP) -- For all its fraught politics and geopolitical import, the Iran nuclear agreement offers something very personal for Sen. Dick Durbin of Illinois: a chance at political redemption.

Durbin, the No. 2 Senate Democrat, is leading the effort to round up Senate support for the international deal that aims to curb Iran's nuclear program in exchange for billions of dollars in relief from economic sanctions. On the other side is Sen. Chuck Schumer of New York, the No. 3 Senate Democrat, who outmaneuvered Durbin earlier this year to win retiring Minority Leader Harry Reid's blessing to be Democrats' next leader - a very public embarrassment for Durbin.

This time, though, Durbin is on the winning side. And to the surprise of many, supporters of the Iran deal are piling up enough votes that they may even be able to block a resolution of disapproval in the Senate next month, meaning President Barack Obama wouldn't have to use his veto pen - an outcome that looked all but inconceivable in the days after the deal was signed July 14.

"Dick stepped up in a big way when the caucus and the president and those of us who support the agreement needed him," said Sen. Chris Murphy, D-Conn. "And his effort has really been critical to the momentum heading in the right direction."

It's still possible that Democrats will fall short of the 41 votes needed to filibuster the disapproval resolution and settle for the 34 needed to sustain Obama's veto, which was the original goal. Durbin declines to predict the outcome.

But for the 70-year-old four-term senator, the Iran deal has been a welcome opportunity to shine after the unsavory palace intrigue with Schumer, Durbin's former longtime roommate in a row house on Capitol Hill. It's allowed him to prove his vote-counting chops as the Democratic whip, the lawmaker charged with lining up support from fellow Democrats. And Durbin hopes that in the process he's strengthened his grip on the whip's job against a possible challenge from Democratic Sen. Patty Murray of Washington, who could make a play for support from fellow female senators.

"I've been whip now for a number of years on the Democratic side, and what I'm doing with this issue I've done 100 times, but rarely with an issue of this importance and rarely if ever over an August recess," Durbin said in a phone interview with The Associated Press from Springfield, Illinois.

"So for those colleagues who want to know if I'm still up to being whip, I think I'm indicating to them that I enjoy the job, I hope to continue in this capacity, and I hope they'll support me when the time comes."

Schumer and Murray declined interview requests, and Schumer's aides have repeatedly denied that Schumer is whipping senators against the Iran deal, saying that the phone calls he's made have been to apprise others of his stance against the agreement, not twist their arms.

Still, opposition from Schumer, the most influential Jewish lawmaker, was seen as having the potential to move other Democrats against the deal, which faces vehement opposition from Republicans and from Israeli leaders who fear it will only empower an enemy sworn to their destruction.

In the days since Schumer announced his opposition to the deal Aug. 6, only one other Democratic senator has done the same, and that announcement from Sen. Robert Menendez of New Jersey was expected. On the other side, the number of Democrats and independents supporting the deal reached 30 as of Friday.

It's not clear why ferocious lobbying against the agreement by pro-Israel groups has not been more effective, but even high-profile Republicans credit the White House-backed campaign on behalf of the deal with yielding results.

At the center of that effort is Durbin, who has been working the phones daily throughout Congress' August recess, even making calls while he and his wife babysat their 3-year-old twin grandkids at home in Springfield. The affable lawmaker said his effort has been more about informing than demanding commitments.

"If a member says there's concern over an issue, then I'm on it," he said.

Durbin knows first-hand that it can be an agonizing decision, especially for lawmakers who represent large Jewish communities. Some of his own supporters are deeply distressed with his stance.

"I'm disappointed and I believe many others are," said Larry J. Hochberg, a Chicago businessman active with pro-Israel groups who said he's supported Durbin in every election but can't say if he'll do so again. "He's a respected fellow, he's been around for a long time, but I think it's a poor legacy for him to leave."

Durbin's role on the Iran deal comes at the same time he is trying to install a protege, Democratic Rep. Tammy Duckworth, in Illinois' other Senate seat, where incumbent Mark Kirk is seen as perhaps the most vulnerable Republican in the Senate.

There, too, he's gotten crosswise with some of his most reliable constituents, black supporters who would like to see a black Democrat in the seat once held by Obama and question Durbin's early endorsement of Duckworth, a double-amputee Iraq War veteran.

In his defense Durbin noted that he was an early backer of Obama, "so my feelings about African-American involvement in the leadership of Illinois and the Democratic Party are pretty well established."

By AP