× Expand (Photo By Tom Williams/CQ Roll Call) (CQ Roll Call via AP Images) Democratic Senator Charles Schumer, left, has pledged support to Republican Senator Bob Corker, right, for a bill designed to scuttle the Obama administration's agreement with Iran over the development of nuclear technology. Here, the two are pictured in the House chamber before Israeli Prime Minister Benjamin Netanyahu's address to a joint meeting of Congress, March 3, 2015.

A week and a half ago, Chuck Schumer, currently third in the leadership of the minority party in the U.S. Senate, moved quickly to solidify his position as the next leader of Democrats, securing the support of his caucus.

This week he endorsed Republican Senator Bob Corker's bill, which, on paper, gives Congress the right to approve the nuclear agreement hammered out with Iran by the U.S. and its allies (collectively known as the P5+1). In reality, this bill is yet another carefully crafted attempt to thwart a negotiated end to this nuclear standoff.

Schumer told Politico: "I strongly believe Congress should have the right to disapprove any agreement, and I support the Corker bill, which would allow that to occur."

The ramifications of the Corker bill are clear. Republicans will not grant their stamp of approval to any treaty signed with Iran. Regardless of their rhetoric, in the absence of a negotiated agreement, the neoconservative dream of military action against Iran creeps closer to reality.

Thus in his first major public act following the announcement of his presumed ascension to the top Democratic position in the Senate, Schumer undermined the views of the overwhelming majority of Democrats across the country, in particular the left flank of the party, whose activism (and online contributions) he will in part rely on to recapture the majority in the 2016 congressional elections.

Progressive groups, including MoveOn, CREDO, Democracy for America, Daily Kos and USAction, have already lined up to warn of severe consequences to those who oppose the president's Iran policy writing in an open letter to Democratic leaders, as reported Wednesday by Politico:

A historic vote on a nuclear deal with Iran is coming. Like the 2002 vote to give President George W. Bush authorization to invade Iraq, Democrats who end up on the wrong side of it will have to answer for their decision for the rest of their careers.

The question is not whether Bob Corker's bill will receive 60 votes in the Senate; that is all but certain. At issue is whether Republicans can build enough Democratic support to override the president's veto.

Senators with a D after their names should take heed of the warning progressive groups sent and look to history, aware that this vote, if successful, will become a critical demarcation point in their careers, equivalent to the October, 2002, vote to authorize war in Iraq. Twelve and a half years later, the ramifications of that vote are still echoing in the Democratic Party.

Howard Dean would have been unlikely to rise to prominence among the Democratic electorate had John Kerry, John Edwards, or Dick Gephart voted against the Iraq War. Dean certainly would have never achieved the public base of support that propelled him to the chairmanship of the Democratic National Committee.

Had Kerry voted differently, Democrats in 2004 would never have to suffer through his contorted explanations as to why even though he voted to authorize military action, he actually opposed going to war in Iraq. This same confusion led Kerry to explain his war-funding vote with the infamous, campaign-killing gaffe that he "voted for it, before he voted against it."

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In 2008, the ghosts of the Iraq vote once again played on the minds of Democrats. To a certain percentage of primary voters, the Iraq War vote, created an irrevocable breach of trust with both Hillary Clinton and John Edwards. Barack Obama, who was not in the Senate at the dawn of the Iraq War, could look back upon that moment with 20/20 hindsight, no baggage, and facing no tough questions about his voting history.

Even as Clinton's 2016 campaign launches with overwhelming support among Democrats, there is still a segment of the party that will always distrust her because of that singular vote.

The 28 Democrats who voted in favor of the Iraq resolution also allowed Republicans to cast some of the blame for the Iraq War on Democrats. On the ten-year anniversary of the invasion, Joe Scarborough claimed on his MSNBC show: "The very same people who spent years beating up George Bush were the very ones beating the drum for Iraq's regime-change and Saddam's ouster."

He specifically cited Hillary Clinton and John Kerry, highlighting their statements before the Iraq war and after things went south.

Bob Corker's bill, more than a decade later, presents Democratic senators with a vote that will define them for decades to come. Progressives are by nature nuanced thinkers, but issues of war and peace-in particular, after the experience of Afghanistan and Iraq-are seen in black and white terms.

For such Democratic senators as Corey Booker, Kirsten Gillibrand, and Amy Klobuchar, who purportedly have ambitions for higher office, this vote could be one that permanently casts them with a scarlet letter among the Democratic electorate.

This is also a defining moment for Chuck Schumer. Right now, if there is a vote to override the president's veto, he can choose between two paths. On the first, he can thumb his nose at the base of the party, while asking them to support his ascension to minority leader. His other choice is for him to reverse course, recognizing that leading our country towards another war in the Middle East is not an acceptable option.