Good Tuesday morning. Here are some of the stories making news in Washington and politics today.

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• Iran announced on Monday that it would soon violate a central element of the 2015 nuclear deal — by producing more uranium than allowed — unless it gets European help to offset the effects of American sanctions. The White House, in turn, ordered another 1,000 troops to the Middle East.

• President Trump had said North Korea and Iran could be convinced to give up their nuclear weapons programs. He is learning that it’s not so easy.

• Confused about the back-and-forth over the Iran deal? Here’s an explainer.

• When Mr. Trump rode down that escalator four years ago, his candidacy seemed like a sideshow. Today he kicks off his re-election bid as the dominant force in politics, and voters will decide before long whether 2016 was a fluke or a transformative moment.