Candidates running for the US Senate in next month's midterm elections have taken to the debate stage over the past few weeks - with some heated exchanges and stinging personal attacks.

As the 3 November election approaches and parties fight for control of Congress, some clear themes have emerged, particularly within some of the hotly-contested Senate races. Here's what you need to know.

Republicans running for office are facing the same question they have been asked in elections since 2016: how aligned are they with President Donald Trump? Conservatives who have bucked the president in the past have generally not fared well with voters.

The president has seen low approval ratings in recent months, with polls suggesting voters are largely concerned with the cost of living and high fuel prices.

While some Republican candidates have remained in lockstep with Trump, a Reuters analysis indicated that two-thirds of candidates in competitive US House and Senate races have broken with the president in some way this election cycle.

Susan Collins, a Maine Republican running for her sixth term in the Senate who has repeatedly broken with Trump, is again putting clear distance between herself and the president.

"I voted with President Biden 91% of the time," Collins said during a debate last week.

"The fact is, this year alone, this Congress alone, I voted against President Trump 137 times," she said.

Collins is fighting a tighter Senate race than she expected against Democrat Troy Jackson, the former president of the Maine Senate. A New York Times/Siena University poll from mid-September suggests Collins could be ahead in that race by 3%, while others indicate Jackson is in the lead.

Elsewhere, some Republican candidates are choosing to separate themselves from the Trump administration's specific policy decisions, while expressing loyalty to Trump himself.

In Iowa, traditionally a Republican stronghold, Congresswoman Ashley Hinson is facing a tougher-than-expected challenge in her Senate race.

She is taking on Democrat Josh Turek, and some polls suggest he has a narrow lead.

Hinson has not gone as far as Maine's Collins in separating herself from Trump, but she has broken with the president on some policy points.

During a 13 October debate with Turek, Hinson was asked about the Trump administration striking a deal with Russia to import 300,000 tonnes to the US, followed by several other shipments.

The Republican candidate did not mince her words: "We need to lower gas prices in this country, we need to lower diesel prices, but I don't think we need to be making a deal with Russia to do it."

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IN DEPTH: The Republicans walking a Trump tightrope EXPLORE: Where the US midterms will be won and lost NEWSLETTER: Sign up for Anthony Zurcher's analysis in your inbox As they have debated in recent weeks, the candidates haven't held back on deploying pointed personal attacks against their opponents.

The race for the vacant Michigan Senate seat - between rivals Abdul El-Sayed, a Democrat, and Mike Rogers, a Republican - has seen its fair Rogers, a Trump-backed former congressman, questioned during a debate whether anyone in his Muslim opponent's family might be on a "watchlist".

El-Sayed, who would be the first Muslim member of the US Senate, pushed back strongly.

He called the Republican "a sock puppet for the Trump administration" and said he was "weak, cowardly [and] won't stand up until his poll numbers drop".

On Thursday, as a protester interrupted a Maine debate between Jackson and Collins, who suggested that the person interrupting the debate was associated with her opponent. Jackson then said to Collins: "Oh shut up, I don't even know that kid."

Further south in Georgia, more personal attacks were exchanged between incumbent Democratic Senator Jon Ossoff and Representative Mike Collins, a Trump-backed Republican.

What started as an exchange where Ossoff accused Collins of taking money out of Georgians' hands to give to data centre developers, quickly turned into a hurling of insults that included Ossoff calling Collins a "bigot" who has "hired half the Third Reich".

Incendiary posts on social media from Collins' son-in-law, David Alan Scheer II, have become a point of contention in the race. In one post, Scheer blamed "Israel and Zionist Jews" for policies he said were intended to "undermine the white, Christian nature of America".

Collins defended himself by accusing Ossoff of "spewing" "craziness".

"I've condemned racism, antisemitism, hate; I don't care where the source is," the Republican said.

There are 35 Senate seats up for grabs this November, but in 21 there are no debates scheduled among the main candidates, an ABC News analysis found. One race's lack of debates has surprised many observers: the Texas contest between James Talarico, a Democratic state representative, and Ken Paxton, a Republican and former state attorney general.

Polls in the typically Republican state suggest that Talarico could be in reach of a surprise win.

Should he succeed, he could help give Democrats control of the US Senate by flipping one of the four seats they need to create a majority. Talarico has accepted four debate invitations from different news networks.

Paxton, meanwhile, has not accepted any of those invitations. In July, Paxton's campaign spokesperson told media outlets that he would debate Talarico. But since then, the campaign, and Paxton, have said little on the matter.

Trump, who backed Paxton in the Republican primaries, has even urged the candidates to debate.

"One thing about not showing up is you lose the opportunity to make the case for yourself, and instead, what you do is you give your opponent the ability and the opportunity to make your case as negative as possible," Peter Trumbore, a political science professor at Oakland University, told the BBC's US partner CBS News last month. Follow the twists and turns of Trump's second term with North America correspondent Anthony Zurcher's weekly US Politics Unspun newsletter. Readers in the UK can sign up here Those outside the UK can