President Donald Trump will soon be on the receiving end of something he didn’t see much from a Republican-led Congress: orders, backed up by subpoenas, for officials to answer questions on controversial policies like the dispatch of thousands of troops to the U.S.-Mexico border.

"Two can play that game!" Trump wrote Wednesday on Twitter.

Now that Democrats have won control of the U.S. House of Representatives, they will be able to force administration officials to testify and provide documents. That will subject Trump’s decision-making -- as well as his personal finances and potential conflicts of interest -- to deeper public and private examination by key committees, as the national focus shifts to the 2020 presidential election.

“The American people voted to give the House of Representatives a mandate to conduct credible, independent, robust, and responsible oversight of the Trump administration,” said Representative Elijah Cummings of Maryland, who is likely to be the Oversight chairman.

The president said on Twitter: "If the Democrats think they are going to waste Taxpayer Money investigating us at the House level, then we will likewise be forced to consider investigating them for all of the leaks of Classified Information, and much else, at the Senate level."

If the Democrats think they are going to waste Taxpayer Money investigating us at the House level, then we will likewise be forced to consider investigating them for all of the leaks of Classified Information, and much else, at the Senate level. Two can play that game! - Donald J. Trump (@realDonaldTrump) November 7, 2018

Democrats say that when it comes to the administration’s response, for example, to the “caravan” of Central American immigrants, they want answers about the rationale behind the troop deployments and details on the force’s rules of engagement.

“It’s not like we’re going to go drunk-crazy with subpoenas. But it may seem that way because we are coming off a two-year drought of no subpoenas,” said Representative Gerald Connolly of Virginia, the top Democrat on the Oversight subcommittee on government operations.

Democrats say they want to pursue unanswered questions about Russian interference in the 2016 election and end what they call a campaign by House Republicans to undermine Special Counsel Robert Mueller’s continuing investigation. But Democratic leaders also play down Republican predictions that they’re out to impeach the president.

Hands-Off Republicans

For the past two years, Republicans have subjected Trump to relatively little oversight, spurning most requests from the minority party. Democrats say that will change almost immediately when the 116th Congress opens on Jan. 3. They have a very long list of topics they plan to look into, including financial deregulation, Trump’s business interests and Russia’s election interference.

Representative Adam Smith of Washington state, who is likely to become chairman of the Armed Services Committee, has made it clear one of the first topics he wants the new Democratic-held House to hold hearings on is troop deployments to the Mexican border.

Smith and more than 100 other current House Democrats have already sent a letter to Defense Secretary James Mattis seeking a response. They contend the president is exploiting a humanitarian issue for “political gain.”

So far, the administration has ignored their questions. Next year, Democrats will have the power to demand that the defense secretary answer such questions in public.

Khashoggi’s Death

The top Democrat on the House Intelligence panel, Adam Schiff of California, has pushed for answers on the administration’s response to the killing of U.S.-based journalist Jamal Khashoggi by Saudi operatives in Turkey.

“I do think we need the Intelligence Committee to do a deep dive -- a probe,” Schiff told ABC News last month. “We also also have to determine whether financial motives are motivating the president and the first family.”

Republican already are sounding warnings about obstructive partisan abuses and threats, saying the Democrats will harass and try to immobilize the Trump administration in the guise of congressional investigations.

Mark Meadows of North Carolina, the Republican who is now chairman of the Oversight subcommittee on government operations and a close Trump ally, said he respects Cummings and will be willing to work with him on “true oversight.”

But Meadows said he fears “there will probably be a lot more subpoenas issued for fishing expeditions that may or may not be based on anything but speculation.”

Republicans point to comments like those from Democrat Maxine Waters of California, a favorite Trump target of ridicule, who is likely to head the Financial Services Committee. She has said that when she takes that panel’s gavel, it will be “payback time” for Wall Street, banks and insurance companies.

Her office hasn’t provided an more precise explanation. But she has included among her pursuits the administration’s financial deregulation efforts, housing issues, and financial ties between Trump and his family with Deutsche Bank AG and Russia.

Russia Probe

Schiff said he also he plans to reopen parts of the Intelligence panel’s Russia-election interference inquiry that Democrats say was prematurely closed by Republicans. Much of what his panel does could depend on the timing and content of Mueller’s report. Democrats say questions remain about Russian money laundering and Trump’s businesses.

And other Democrats, including Jerrold Nadler of New York on Judiciary and Richard Neal of Massachusetts on Ways and Means, have their own lists of anticipated inquiries.

The Ways and Means panel, for example, has the authority to compel Trump to hand over his long-sought tax returns. The members aren’t allowed to release them publicly, though.

More broadly, Democrats want to scrutinize the multiple ethics scandals involving administration officials, including most recently Interior Secretary Ryan Zinke, who is under investigation for his travel and business ties.

Among other topics they plan to look into are whether top-secret security clearances are being handled properly and how to control rising prescription drug and health-care prices.

Broad Authority

Congress has broad constitutional authority to conduct oversight and investigations, a power that has been upheld in numerous Supreme Court cases, some of them dating to issues arising from the Teapot Dome scandal of the 1920s. The majority party in the House controls almost all of the subpoena power and other investigative tools.

Republicans complain that Democrats are mostly interested in assembling a case to impeach Trump.

“I do think they will definitely try to impeach almost immediately,” said Meadows, even though Minority Leader Nancy Pelosi and other Democratic leaders have downplayed that issue during the campaign.

Pelosi suggested that the new majority’s emphasis will be more about traditional checks and balances than investigative excess.

"In a stark contrast to the GOP Congress, the Democratic Congress will be led with transparency and openness so that the public can see what is happening and how it affects them," she said in a victory speech to Democrats on Tuesday night.