Now that special counsel Robert Mueller has finished his investigation into the Trump campaign and Russian involvement in the 2016 US election, congressional Democrats are taking the baton, gearing up for a series of investigations into the President and his administration.

Those investigations, like Mueller's, will provide key insights into issues of obstruction, corruption, and abuse of power, much of which has been happening in plain sight. But like the still-unreleased Mueller report, they will also show how limited checks on presidential power are, and how dangerously powerful the executive has become.

That power is not new. Much of the past 50 years has been a battle over how to rein in the imperial presidency, which was so clearly on display during the presidency of the Nixon administration. But while many people have been thinking about that administration in recent years, particularly the Watergate investigations that led to Richard Nixon's resignation, they have seldom turned their attention to what happened after: how Congress attempted to limit presidential power, and how it ultimately failed.

Invigorated by the "Watergate babies", the group of young, reform-minded Democrats swept into office after Nixon's resignation, Congress took up a raft of legislation aimed at curtailing the power of the presidency.

Watergate exposed an administration riddled with criminality. The presidency, many Americans agreed after, had grown much too powerful, culminating in the mindset Nixon brought into office and later shared with journalist David Frost that anything the president did was, by definition, legal.

The idea that the president was above the law was precisely what journalists and Congress sought to disprove in the years that followed Watergate. Journalists inspired by the investigative reporting of Bob Woodward and Carl Bernstein sought to unmask wrongdoing in government, reviving the notion that the media should be a check on political elites.

But it was in Congress where the real victories were won. Invigorated by the "Watergate babies", the group of young, reform-minded Democrats swept into office after Nixon's resignation, Congress took up a raft of legislation aimed at curtailing the power of the presidency.

The list of reforms was breathtaking: laws to combat domestic spying, to reform election finance law, to curb presidential war powers, to end government secrecy, to limit national emergency powers, to preserve presidential records, and to create an independent counsel who could investigate executive wrongdoing. Again and again Congress sought to reassert its power, and by extension, the public's.

But it turned out the presidency was more powerful than even these reforms. Nowhere was this more clear than in the 1980s, when a massive international scandal roiled the Reagan administration. The Iran-Contra affair involved countless illegalities: millions of dollars in forbidden support to militants in Nicaragua, illegal arms sales to Iran, and a cover-up that reached all the way to the Oval Office.

It was the first test of the post-Watergate reforms. Congress, which had passed several laws forbidding any support to the Contras, immediately held hearings. Lawrence Walsh was appointed as an independent counsel and given free rein. Though the administration immediately violated the Presidential Records Act, which mandated that all documents be preserved – one of the main conspirators held a "shredding party" to destroy mountains of incriminating evidence – Walsh amassed enough evidence to indict 14 people, including high-level members of the administration, and win convictions against 11 of them.

The Attorney-General, chosen in large part because he opposed the Mueller investigation, can block its release; so far he has produced the only glimpse into the report we've seen, a four-page summary that has drawn sharp condemnation from members of the Mueller team for inaccuracies.

Yet Walsh proved no match for the presidency. Reagan and his vice-president and successor, George H. W. Bush, refused to hand over evidence and, when Bush lost his bid for re-election, he pardoned just about everyone.

It was one of the most serious abuses of power in American presidential history, and neither Reagan nor Bush paid a price for it.

Nor was Iran-Contra an outlier. Presidents have continued to have spectacular autonomy when it comes to war-making, ignoring the War Powers Act by using the military without declarations of war. Freedom of Information Act requests go unfulfilled for years if not decades, while an ever-growing amount of information gets designated classified, hiding it from public eyes.

The Supreme Court has remade campaign finance so that unlimited money can flow into presidential campaigns with no public disclosure, choking off public oversight while opening endless avenues for corruption.

In many ways, the Trump administration is a monument to just how ineffective checks on the presidency have become. Though Robert Mueller was appointed special counsel (a more limited version of the independent counsel position that existed until 1999) and was able to complete his investigation, there is no mechanism to ensure that his report becomes public.

The Attorney-General, chosen in large part because he opposed the Mueller investigation, can block its release; so far he has produced the only glimpse into the report we've seen, a four-page summary that has drawn sharp condemnation from members of the Mueller team for inaccuracies.

We may one day see the full report; as with Iran-Contra, we will probably never see the administration pay a price for its contents.

Investigations into the current administration will continue, as Congress looks into the President's finances, his cabinet's enrichment schemes, and the many ways Trump has used the presidency to funnel money to his properties and businesses. But given the limits of the special counsel, the breadth of presidential pardon powers, and the weakness of congressional oversight, those investigations are unlikely to curb the imperial presidency, or restore Americans' faith in their government.