– Democrats, transitioning into the House majority, have quietly sent dozens of letters in recent weeks seeking documents and testimony from President Donald Trump’s businesses, his campaign and his administration, setting the table for investigations that could reach the center of his presidency.

Clear targets have emerged in the process, and some others appear to have fallen away, at least for now.

Immigration policy

The impasse over Trump’s proposed border wall and the death late last month of an 8-year-old boy from Guatemala in U.S. custody have catapulted the administration’s divisive policies at the border to the top of House Democrats’ agenda. Rep. Jerrold Nadler of New York, the Judiciary Committee chairman, and a handful of other chairmen plan to examine immigration policies.

Their interest and detailed questions could prove problematic for Trump’s efforts to make a case for his border wall, shining a light on gaps in the current policy and trying to highlight the human toll on migrants.

“We are calling on [the Department of Homeland Security] to preserve any and all evidence related to these horrible incidents,” the chairmen wrote. “We as a country can and must do better.”

Nadler has already invited Matthew Whitaker, the acting attorney general, to be the committee’s first public hearing witness, and indicated in recent days that he would subpoena Whitaker if necessary to compel an appearance before the end of the month.

Russia

After seething over Republican use of the House Intelligence Committee to turn an investigation of Russian interference in the 2016 election into an attempt to discredit the president’s investigators, Democrats plan to quickly flip the lens back on to Trump and his campaign itself. But the panel’s leaders have cautioned that their approach will be narrower than once predicted.

The panel’s new chairman, Rep. Adam Schiff of California, said it was initiating a request for phone records of the president’s eldest son, Donald Trump Jr., to clarify whom he called while arranging a June 2016 meeting at Trump Tower in Manhattan between members of the Trump campaign and a Russian lawyer. Phone records already in the hands of congressional investigators show a call was placed to a blocked number, and Trump Jr. told investigators that he did not remember who he had called. Democrats believe the blocked number may have belonged to his father.

The committee would also like to request financial records related to Trump’s dealings with Russia and other foreign powers, but that ultimately may have to rope in the House Financial Services Committee.

Trump’s tax returns

Democrats tried more than a dozen times over the past two years to obtain Trump’s tax returns. But now that they finally have the opportunity to do so — thanks to an obscure 1920s tax code provision — the relevant Democratic committee chairman appears to be in no rush.

In an effort to parry Republican accusations of overreach, the House Ways and Means chairman, Rep. Richard Neal of Massachusetts, has decided instead to try to first build a public case for why the returns ought to become public before he lodges a formal request.