WASHINGTON - The Democratic Party's chances in the November mid-term elections have been buoyed by their hot streak of legislative victories this month, although Republicans remain broadly favoured to retake the Democrat-held House of Representatives and, more narrowly, the Senate.

President Joe Biden's job approval ratings have also improved from their low in July, while former president Donald Trump is being weighed down politically by congressional investigation into his role in inciting the Jan 6 attack on the Capitol.

"Legislative successes, a drop in gas prices, continued headlines about former president Donald Trump, and a slate of weak Senate candidates are harming Republicans' chances of winning a Senate majority and slightly reducing their odds of taking the House," analysts from the Eurasia Group political consultancy wrote in a note last week.

The party of the incumbent president traditionally loses votes in mid-term elections, which are held halfway through a presidential term and viewed as a referendum on his leadership and politics.

But some signs point to this backlash being smaller than usual, albeit with the caveat that the political situation remains fluid - much can happen between now and polling day on Nov 8.

Democrats achieved an unexpected hot streak in Congress in August, peaking with the passage of the Inflation Reduction Act, a massive climate and taxes package.

Their victories also included bipartisan legislation that boosted domestic semiconductor manufacturing and extended health benefits for veterans, as well as Mr Biden's executive action to forgive student loan debts, although that plan will run into legal challenges.

Democrats have also successfully seized on the rise of abortion as a galvanising concern among voters, following the June 24 Supreme Court decision to overturn a 49-year-old constitutional right to an abortion, and focused on Mr Trump's troubles surrounding the Federal Bureau of Investigation's search of his Mar-A-Lago home.

Various analyses of primary elections so far have concluded that Democrats are performing better than expected, even in races they lost, and turning out in higher than usual numbers.

An Aug 2 statewide referendum in conservative Kansas, in which people voted to keep abortion legal, was also seen as a setback for Republicans and a signal that their anti-abortion agenda was not as popular as hoped.

"Democratic voters are starting to show enthusiasm both in polling and a surprising Kansas referendum, reversing a large enthusiasm gap that was evident earlier this year and in off-year elections in Virginia and New Jersey last year," said the Eurasia Group analysts.

The non-partisan Cook Political Report last week revised its prediction of Republicans gaining 20 to 35 seats in the House to 10 to 20, and said it was not out of the question for Democrats to maintain control.

Mr Biden seized on these trends in a fiery speech at a campaign rally on Thursday (Aug 25), giving a preview of the Democrats' fall campaigning strategies - touting their victories and mobilising voters to turn out in protest against extremist Republicans and the Republican Party's push to curtail abortion access.

"They're a threat to our very democracy. They refuse to accept the will of the people. They embrace... political violence," he said, calling it a philosophy akin to "semi-fascism" that went beyond Mr Trump himself.

Democrats, nonetheless, will face an uphill battle in the House. Even if inflation has peaked, high prices will be felt by voters for some time.

And they are very unlikely to maintain their wafer-thin control of the Senate, where 35 seats are up for election - 14 held by Democrats and 21 by Republicans.

The jury, moreover, is still out on whether Mr Biden will help or hurt his party colleagues' chances. A Morning Consult-Politico survey released on Wednesday found his job approval rating improving, reaching 43 per cent in mid-August compared with his record low of 37 per cent a month ago, and the highest since May.

The poll found, however, that a 55 per cent majority of voters still disapprove of him, though this was down from a 59 per cent high.