All 221 Republicans backed a formal impeachment hearing of President Joe Biden in one of the last votes cast by the US House of Representatives before members travelled home for winter break.

Republican leaders obtained the unanimous support they sought, but it was more politically perilous for some lawmakers than others. Vulnerable Republicans representing divided districts will now have to defend their support of an investigation that many of their constituents could consider deeply partisan.

BBC News contacted the 17 Republicans representing districts that President Biden won in 2020. Political analysts and pollsters - as well as Democratic opponents - believe these House members to be at most risk of losing their seats ahead of the upcoming 2024 US election.

How these House members walk this political tight-rope over Mr Biden's impeachment inquiry could help decide whether Democrats or Republicans control the House of Representatives next year, they said. It's a particular challenge with Republicans maintaining a razor-thin majority in the House.

"It's a problem, because they're already facing an uphill battle in a swing district," said Dan Judy, a Republican pollster with North Star Opinion Research.

The push to impeach Mr Biden stems from Republicans' years-long investigations into his son, Hunter Biden, who they have accused of using his father's name to pursue illegal or unethical business dealings.

While Hunter Biden was recently charged by the Justice Department over tax violations, months of Republican investigations have seemingly failed to implicate the president in related wrongdoing.

Mr Judy warned swing or independent voters who his party needs to win over could question whether "an impeachment inquiry is the best use of the government's finite time and resources".

Most of the lawmakers appeared to understand that calculus and shared cautious statements or remained silent when asked about the vote. Those who spoke up framed their decision not as a full-throated endorsement of impeaching Mr Biden, but as a vote in favour of granting the House greater investigatory power.