House Minority Leader Nancy Pelosi speaks during a news conference on Capitol Hill this month. (Susan Walsh/AP)

In January, when Democrats take control of the House, how will they oversee and investigate the Trump administration? When the parties divide control of government, lawmakers typically scrutinize the executive branch more aggressively — particularly when the parties are as intensely polarized as they are now.

Some observers warn Democrats not to push too far too fast, lest they risk a backlash. But a coherent, vigorous investigative strategy can erode President Trump’s support, leading to policy and political gains for the Democrats.

Let’s look at both the opportunities and difficulties Democrats will face in overseeing the Trump administration.

1. Investigations can reshape politics and policy

Our research suggests three ways that investigations can affect politics and policy. First, investigations can spur Congress to enact new legislation. For example, a Republican Congress would probably not have enacted sanctions against Russia over Trump’s objections had the House and Senate intelligence probes not created political pressure for action.

Second, presidents sometimes make policy concessions in hopes of warding off more extreme congressional action. For example, in the mid-1970s, Congress’s Church Committee revealed that the intelligence agencies had systematically abused their powers, including eavesdropping on civil rights leaders at home and toppling unfriendly regimes abroad. Outraged, the public pushed Congress to take action. Hoping to preempt far-reaching restrictions, President Gerald Ford issued an executive order in 1976 banning political assassinations and reorganizing the intelligence apparatus.

Third, investigations can erode the president’s public standing and weaken him politically — which then makes it harder for him to gain support for his policies. By analyzing all congressional investigations between 1953 and 2014, we found that congressional probes — even those led by the opposition — systematically lower public approval of the president. Consider the 1987 congressional investigation of the Iran-contra affair, in which the Reagan administration secretly sold arms to Iran and covertly channeled the profits to Nicaraguan rebels. While President Ronald Reagan avoided impeachment, the investigation weakened his political power and undermined his influence on Capitol Hill.

2. Polarized parties may limit the effects of investigations

Investigations have long been highly partisan, but many of the probes that had the most impact secured at least some cooperation and even support from the other side of the aisle. When investigations succeeded in triggering new legislation, this bipartisan support was critical. Presidents were also more likely to make concessions when investigations generated calls for change from at least some members of their own party.

But given today’s extremely polarized climate, few expect much bipartisan support for new investigations. Over the last two years, most Republicans have publicly supported President Trump even when his words and deeds have pushed past long-held norms. And House Republicans jockeying for leadership roles on key committees are emphasizing their zeal to defend Trump from Democratic attacks. As a result, new investigations may struggle to build political pressure for legislation or for presidential policy concessions.

In the 1980s, House Democrats slowed Reagan’s effort to undo environmental regulations by holding high-profile hearings into allegations of conflicts of interest, sweetheart deals for favored industries and other abuses of power at the Environmental Protection Agency. These revelations and the EPA’s refusal to turn over documents led the media to dub the scandal “sewergate” and turned public opinion against the president. In the face of mounting pressure, Reagan reversed course and made significant policy concessions.

Would such a strategy work today? Democrats have plenty of potential targets. Trump has sought to roll back a range of environmental, land use and financial regulations. He has appointed department heads who have been accused of conflicts of interest or misuse of public funds. But without Republicans willing to break with the administration as we’ve seen in the distant past, and with a more polarized news media, the Trump administration will have an easier time staying the course.

3. Galvanizing media attention and inflicting political damage

Investigations may still have an impact if they can further sway public opinion against Trump and cost him political capital. Garnering sustained media coverage will make or break Democrats’ oversight strategy.

Republican efforts to investigate alleged scandals in the Obama administration — such as Solyndra and Fast and Furious — generally failed to secure widespread public attention. Although Fox News and other conservative outlets gave Republicans prominent coverage, most media outlets concluded that evidence of wrongdoing was too flimsy for substantial attention.

In contrast, the Benghazi investigation had enormous indirect consequences. Investigators ultimately found little concrete evidence of wrongdoing. However, the committee’s almost accidental discovery of Hillary Clinton’s private email server triggered an FBI investigation and an avalanche of sustained media coverage that may well have cost Clinton the presidential election.

Targeted investigations of administration officials and actions in the EPA, departments of Commerce and Interior, and elsewhere may fail to produce a Clinton-email-level “bombshell.” But if they uncover clear evidence of corruption or abuse of power, they should attract significant media coverage — even without GOP support — painting the administration in a bad light. This could lead to policy concessions — not because legislative action was imminent — but to stem the tide of costly critical coverage.

Less policy-focused but more sensational probes, such as demanding Trump’s tax returns and investigating his possible payoffs to women he has allegedly had affairs with, would generate juicy headlines. But Democrats must balance the political gains from such coverage against the risk of voters perceiving investigators as serving partisan, rather than public, interests.

4. The perils (and potential) of impeachment politics

Finally, many Democratic voters want investigators to focus on explosive allegations that the Trump campaign conspired in Russia’s efforts to influence the 2016 election and obstructed justice, the focus of special counsel Robert S. Mueller III’s investigation.

And if Trump moves against Mueller, Democrats would no doubt try to convince the public that Trump has abused his power and would push to have Mueller’s discoveries released publicly.

When President Richard Nixon fired the Watergate special prosecutor, enough dissenting Republicans refused to treat Watergate as politics as usual. It’s hard to imagine a similar response from Republicans today.

Nevertheless, if House Democrats believed the president was genuinely endangering the rule of law, they might still pursue impeachment. But with the country almost evenly divided on impeachment, investigators must uncover enough new revelations to move the needle — a daunting challenge given most partisans’ reluctance to change their opinions given new information — or risk triggering an all-out partisan war where all bets are off.

Douglas Kriner is a professor of government at Cornell University. 

Eric Schickler is the Jeffrey & Ashley McDermott professor of political science at the University of California at Berkeley. 

They are the authors of “Investigating the President: Congressional Checks on Presidential Power” (Princeton University Press, 2016).