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

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• President Trump said he planned to impose a 5 percent tariff on all imported goods from Mexico, a tax he said would “gradually increase” until Mexico stopped the flow of undocumented immigrants across the border. The threat was a drastic move against an American ally, essentially daring the Mexican government to risk economic catastrophe on both sides of the border if it did not capitulate to his demands.

• Amid criticism of the special counsel’s investigation, Mr. Trump offered an extraordinary admission in a tweet: He acknowledged, for the first time, Russia’s “helping me to get elected.” He then abruptly denied it again, seeking to counter increasing calls for impeachment.

• Some Democrats say opening an impeachment inquiry could help the House overcome the president’s blockade of its investigations. But others say it could backfire politically. Here’s how impeachment works, and what you need to know about it.