Significant gains for the Democrats will embolden the party and raise hope that Trump could be defeated in 2020, writes David Millward
After Pennsylvania, a sense of panic sets in among Republican strategists
In terms of the balance of power in the US Congress, the victory earlier this month of Democrat Conor Lamb in the Pennsylvania special election will have minimal impact given the Republicans' comfortable majority in the House of Representatives.
But it has generated a measure of panic in the GOP, which is reeling from the impact of losing a seat it should have held comfortably. After all, Donald Trump took the district by a massive 20 points in the presidential election.
The Republicans and their deep-pocketed conservative supporters threw almost everything at Pennsylvania’s 18th district. According to Federal Election Commission filings, conservative groups spent $10.7 million on the contest, accounting for 80 per cent of the total from groups outside the state.
The sense of panic among Republican strategists is understandable, especially with the mid-terms only a few months away. Unlike the party’s humiliation in the Alabama Senate election, the Republicans cannot heap the blame on the candidate. Rick Saccone had none of the baggage that brought down Roy Moore.
Trump gave his full support to Mr Saccone throughout the campaign – which was not the case in Alabama.
This was a rust-belt district, typical of those that swept Donald Trump to victory. If the Republicans can lose a congressional seat where it had been a long way ahead, the fear is that a host of others will fall in November. Some senior figures in the party's hierarchy are talking darkly of the result being an alarm call.
This was, of course, an unsubtle plea to conservative donors to dig deep to fund a campaign blitz over the next few months.
On the other side of the political divide, there is no denying that the Democrats are on something of a roll, with high profile victories in Alabama and Pennsylvania being accompanied by a raft of wins at state level. Much has been made of Mr Lamb’s moderation, with his supporters arguing that the party does not need to swing left to win back power.
It is an interesting message given the infighting that followed the 2016 presidential election defeat and the groundswell of grassroots opposition to establishment figures like Dianne Feinstein, who has come under fire from left-wing activists.
What impact the Democrat resurgence might have on the US approach to the Middle East, Hezbollah and the Iran nuclear deal is hard to gauge, given the extent to which foreign policy is largely dictated by the US president.
Andrew Bacevich, professor of International Relations at Boston University, is sceptical whether a change of guard in Congress will have real significance.
“When it comes to US policy in the Middle East or more generally, who speaks for Democrats? Or more specifically, who possesses the stature and standing to be heard and make a difference?” he says.
“I submit that there is no one. Once upon a time, John McCain was the conscience of the GOP on such matters. The Democrats today have no one to fill McCain's old role.”
Chris Galdieri, associate professor of politics at Saint Anselm College in New Hampshire, takes a slightly different view.
"If the Democrats take the House, but not the Senate, I think you would see much more oversight over what the current administration is doing."
Significant gains for the Democrats will embolden the party and raise hope that Trump could be defeated in 2020.
The prospect of losing power would concentrate Mr Trump’s mind and, given his focus appears to be on trade and North Korea, unwinding the Obama administration’s approach to Iran and the Middle East, may not be top of his list of priorities.