Donald Trump has always made American liberals angry. Now he also makes them fearful. What some fear, in particular, is that Mr Trump’s current popularity – with the US economy growing at an annual rate of 4% – means that his Republican party will see off the Democrats’ challenge in November’s midterm congressional elections, enabling the president, among other things, to try again to dismantle Barack Obama’s affordable care reforms. Even more than that, they fear that he is on course to be re-elected for a second term in 2020.

None of this can be ruled out, especially after the experience of 2016, in which so many expert predictions were confounded. But it is not a preordained outcome. It can be stopped, and American voters have no reason to approach the elections fatalistically. Mr Trump is very popular among his own supporters – he has approval ratings around 90%. But his national approval is very low – 41% in a Gallup poll this week. Since Mr Trump is the most bigoted, misogynistic and jingoistic president in modern times, that may seem a disturbingly high rating. Though history suggests that a president with such ratings in August will see his party pummelled in November, Mr Trump has defied the Democrats in the past, and many still fear he may do so again.

This may be unduly pessimistic if concrete indications of the American mood in a number of special byelections and primaries this week are to be believed. These showed Republican votes consistently down. In a special US Congress election in Ohio, in particular, the Republicans squeaked home in a district that Mr Trump won by 11 points two years ago. Typically, Mr Trump tweeted that this was a great victory. It was no such thing. There are 68 less solidly Republican congressional seats across the US than that one in Ohio; if the Democrats can win 23 of them (one in three) they will regain control of the House of Representatives. On the face of this week’s contest results, that is an achievable aim, but they need to win back a lot of rural swing voters.

If that happens, the House will be able to conduct real oversight hearings, rather than the current phoney ones, into the dark places of the Trump administration, not least in relation to Russia. If the Democrats recapture the Senate at the same time – a much taller order – Mr Trump’s judicial nominations might be blocked too. Mr Trump is certain to fight dirty, because that’s what he does. But in the end, it will all depend on who is motivated enough to turn out to vote, and who stays at home. The evidence of this week is bad for Republicans.

There are less than three months to go before the US midterms. In the next few weeks, the special counsel Robert Mueller is expected to give his verdict on whether Mr Trump and his lieutenants obstructed justice during Mr Mueller’s wider investigation into Russia’s role in the 2016 election. A separate report on the Russian issue itself is likely to follow later. The politics of the midterms – and the remaining part of Mr Trump’s term – will depend in no small way on the Mueller verdicts and the response to them.

This week marked the anniversary of Richard Nixon’s resignation in 1974. Nixon resigned because the supreme court ruled that the president was not above the law and because congressional Republicans abandoned him. It was a victory for the constitution and the rule of law. Right now, it appears likely that the Republican party on Capitol Hill will rally around the president, whatever Mr Mueller says. The elections in November will shape Mr Trump’s future. They may also tell us how far America has changed.