Polls show Trump's party could lose control of Congress but they may be wrong

If the midterm elections polls can be believed, the Democratic Party could be about to seize control of the US Congress.

Polling predicts a crushing victory for Democrats in the House of Representatives, where they need to gain four seats.

There is even the possibility of Republicans losing their majority in the Senate, where the Democrats need to defend four seats in tight races and win four more to wrest back control.

Historically at midterm elections, control of the House can flip. But a path to the Senate for Democrats is quite a turnaround for the party that started out having to "pitch a perfect game", as Jessica Taylor from the Cook Political Report puts it.

Mr Trump's decision to launch a war on Iran has been pivotal in his sliding popularity.

"Typically the president's party loses seats and certainly President Trump's approval ratings were not great before March, but pursuing an unpopular war that drove prices, especially on gasoline and diesel, further up has only put his party in more peril," Ms Taylor said.

Democrats now look competitive in Senate races in red states such as Texas, Kansas, Alaska, Iowa and Ohio.

They are widely considered likely to win a North Carolina Senate seat off the Republicans, and polling is very tight in the swing state of Michigan, which backed Mr Trump in the presidential race two years ago.

But Ms Taylor cautions that polls are only a snapshot of voter sentiment at a moment in time.

"I think this is why we look at polls holistically, rather than one poll, because you can have an outlier ... but we see most of the polls trending in the same direction. I mean, a lot of these polls are just very, very close."

Ms Taylor says Democrats should not interpret the positive numbers as an endorsement.

Many analysts, including the founder of the Cook Political Report, are characterising the numbers as more of a "red undertow" than a "blue wave".

"It's Republicans that are in power and voters have a strong anti-incumbent sentiment right now. It's more like a pox on both their houses," Ms Taylor said.

Many polls are extremely close and within the margin of error (a measure that accounts for how likely it is to be wrong).

This is similar to the 2024 presidential polls, which were mostly too close to call. Mr Trump ended up sweeping all the swing states, but that was not particularly outside what polls had predicted.

"National polls always under count support for Republicans, and with President Trump barnstorming the country and driving our voters to the polls, Republicans are ready to fight, defy history, and protect our majorities," Republican National Committee press secretary Natalie Baldassarre said.

Charles Franklin, the director of the respected Marquette Law School Poll, recently told Politico that one of the largest fears for pollsters was that not enough Republicans were responding.

"We've done a lot over this past decade to try to improve the control we have over those kinds of errors, but ultimately we can't force people to do polls, and so this remains always a background fear factor," he said.

This graph shows how polls have changed this year.

But Republican pollster and strategist Patrick Ruffini said the environment was "genuinely bad" for Republicans.

"They look weaker this late in a cycle than I can remember," he told the ABC.

He said there also were complications with where the Democrats were leading.

"The Senate battleground runs through red states like Iowa, Ohio and Texas and these are states that Republicans consistently carry by solid margins, or that the polls have a hard time getting right."

Mr Ruffini recently examined more than 3,000 Senate polls from the past eight years to assess their track record.

He found 73 per cent of them had overstated the Democrat candidate. In Iowa, Ohio and Michigan, the Democrats were overstated 93 per cent of the time.

"That doesn't mean it will happen again. Democrats are still gaining in the polls this year," he said.

"The bigger risk is uneven error from state to state, where the national picture is right but some states miss.

"Polls have been more accurate in the Sun Belt than in the Rust Belt, so I'd believe a blue Texas before a blue Iowa."

It is not always the Republicans who defy polls. In what the US calls off-cycle elections, the Democrats running in high-profile governor races in New Jersey and Virginia have outperformed their polling and won easily.

Even with the extraordinary unpopularity of Mr Trump, Democrats are reluctant to consider the midterms sewn up.

Former Obama White House chief of staff Rahm Emanuel recently stressed to The New Yorker that he felt only "cautiously optimistic" about the Senate, although he was more confident about the House.

It is possible to read some tea leaves about where money is pouring in.

The analytics firm AdImpact calculated that Republicans were out-spending Democrats in 10 battleground Senate races a week out from the election.

The Republican war chest was significantly boosted by MAGA Inc, a political action committee, or PAC, associated with the president.

PACs are organisations formed explicitly to raise and spend money on election races.

In the final sprint of campaigning, Mr Trump promised that he would unleash a further $US100 million ($142 million) to back Republican candidates, adding to more than $US300 million MAGA Inc had already spent.

Other mega-donors like Elon Musk are also using PACs to put money behind favored candidates.

The closely fought Texas Senate race has been flooded with cash, with spending surpassing $US500 million.

In North Carolina, where the former Democratic governor Roy Cooper looks set to easily convert a Republican Senate seat, the top campaign spending organisation for Senate Republicans pulled its funding at the start of October.

That suggests the party considered the seat lost even then. In Kansas, which has not elected a Democrat senator since 1932, ad spending increased tenfold in the weeks leading up to the election.

Observers are also reading in to Mr Trump's travel schedule. He has mainly held rallies in deeply red areas.

And the president, of course, does not believe the polling.

"Look, the polls are fake," he said last week. "I don't rely on the polls, but polls mean something. But a lot of the polls are rigged, just like the journalists are rigged."