Bob's Blog: The Iran end-game

(CBS News) -- It's the letter read all around the world - literally.

The talk of the town this week in Washington is all about the controversial letter sent by 47 Senate Republicans to the leaders of Iran. The letter warns Iran that any nuclear deal they reach with President Obama could be undone by the next president with the stroke of a pen.

Analysts have debated all week whether the assertions in the letter actually hold true. But I've been more amazed by the letter itself. There are many ways for Republicans to try and stop a nuclear agreement with Iran, including passing new sanctions. It's very different to see nearly half of the Senate interfere in foreign policy negotiations by reaching out directly to leaders of another country.

Sen. Tom Cotton, the Arkansas Republican who authored the letter, joins us Sunday on "Face The Nation" to talk about this. Why did he choose this route? And has it backfired?

Sen. Joe Manchin, D-W.Va., will also weigh in on the effort to prevent Iran from acquiring a nuclear weapond.

Also in Washington, there's another Secret Service scandal. This time involving two senior agents who drunkenly drove through a White House barricade during an active investigation.

And the controversy swirling around former Secretary of State Hillary Clinton continues, with new questions about which emails she kept and which she deleted. Republicans are accusing Clinton of erasing emails that are relevant to their investigation into the 2012 Benghazi attack.

We'll get the latest on these two big stories from Rep. Elijah Cummings, D-Md., who is the ranking member on both the House Oversight Committee and on the Benghazi investigative committee.

And one week after the 50th anniversary of the Selma marches, racial clashes are in the news again.

In Ferguson, Mo., two police officers were shot during a protest against the unfair practices of the police department there. Oklahoma University is still reeling after footage leaked of fraternity members chanting a racist song. And there are still many unanswered questions in Madison, Wis., where an unarmed African American teenager was killed by a police officer.

We'll discuss all these issues with Cornell William Brooks, president of the NAACP, and Sherrilyn Ifill, president of the NAACP Legal Defense Fund.

We'll round out our show, as usual, with our weekly roundtable - and there is much to discuss this time around. Joining us this week are Susan Page of USA Today, Peter Baker of The New York Times, John Heileman of Bloomberg and Dana Milbank of the Washington Post.

We hope you'll tune in. Check your local listings.