Democratic lawmakers taking control of the U.S. House of Representatives in January are vowing to launch wide-ranging investigations of President Donald Trump's business empire and policies he has adopted during the first two years in office.Republicans who have controlled both houses of Congress since the Republican Trump assumed power in early 2017 have largely given him a pass, declining to hold hearings that might reflect badly on him or the officials he has appointed.But Congressman Jerrold Nadler, a New York Democrat once described by Trump as "one of the most egregious hacks in contemporary politics," said the election results show "the American people have demanded accountability from their government and sent a clear message of what they want from Congress." Nadler said Trump "may not like it, but he and his administration will be held accountable to our laws and to the American people."New investigations?Trump told a White House news conference that if Democrats start numerous new investigations, "We're going to do the same thing, and government comes to a halt."He decried, as he often has for months, special counsel Robert Mueller's ongoing investigation into Trump 2016 campaign links to Russia and whether Trump, as president, obstructed justice by trying to thwart the investigation."It's a disgrace," he said. "It's an embarrassment to our country."Two other key Democratic lawmakers, Elijah Cummings of Maryland, who will almost certainly head the House Oversight Committee, and Adam Schiff of the Intelligence Committee, have both called for new oversight of Trump and his administration, probes often blocked by majority Republicans in the past two years."I plan to shine a light on waste, fraud and abuse in the Trump administration," Cummings said Wednesday. "I want to probe senior administration officials across the government who have abused their positions of power and wasted taxpayer money, as well as President Trump's decisions to act in his own financial self-interest."Unilateral subpoenas powerControl of the committees — where the three lawmakers are currently the highest-ranking Democrats — will hand them the unilateral power to issue subpoenas if they wish, as well as to demand documents and testimony from White House officials and important figures in Trump's campaign team and businesses.With control of the legislative apparatus in the House, they will also have more money and staff for investigations.Democrats have called for investigations of Cabinet officials' alleged misuse of taxpayer funds, Trump's immigration policies that have separated hundreds of migrant children from their parents at the U.S.-Mexican border, the handling of last year's Hurricane Maria crisis in the island territory of Puerto Rico, and alleged conflicts of interest between Trump's businesses and his presidency.Some Democrats have also called for starting impeachment hearings against Trump, but mostly appear willing to wait to see what information Mueller produces from his 18-month investigation.Mueller's moveWashington analysts say they expect that Mueller, now that the election is over, will soon release more information from his investigation and possibly indict more figures tied to Trump's 2016 campaign.Trump, well aware of the Democratic intentions to investigate his personal taxes, which he has repeatedly declined to divulge, possible business connections with the government he oversees, and his administration's policies, assailed the looming Democratic-led House probes and the Mueller investigation on Twitter even as he boasted about Republican Senate candidates who ousted Democratic incumbents. Would-be House Speaker Nancy Pelosi, the top Democrat in the chamber, talked about political bipartisanship in a congratulatory call from Trump and has said Democrats could embrace Trump's call for infrastructure spending across the United States to fix crumbling roads and bridges and new regulations to cut the cost of prescription drugs.But Pelosi pointedly told supporters the Democratic victory was about "restoring the Constitution and checks and balance to the Trump administration.It is about stopping the [Republicans] and Trump administration's assault" on two government-run medical insurance programs for older and impoverished Americans "and people living with pre-existing medical conditions."