When the leader of Britain’s opposition, Jeremy Corbyn, surprised his own Labour party by writing a public letter about how he is opposed to air strikes against ISIS (also known as the Islamic State) in Syria — it had a massive impact on his approval ratings.

Although Corbyn eventually gave his party a free vote, instead of whipping around to make sure everyone voted the same way, the impact was so “serious” that the latest YouGov poll, commissioned by The Times newspaper, showed that 65% of respondents think that he is “doing badly” as a leader. Only 24% think he is doing well.

His approval rating has almost halved since November 17.

“Many have been critical of Jeremy Corbyn for prioritising the views of Labour members over those who voted Labour in 2015, and for writing to MPs setting out his opposition to bombing Syria before the shadow cabinet had finalised its stance. This has had a serious impact on his approval rating,” added the polling house in a statement.

Look how terrible the slide is in his approval ratings — and he’s only been the leader of the Labour party since September:

Do not underestimate how terrible the polling results are.

YouGov pointed out that even Corbyn’s predecessor, Ed Miliband, “enjoyed better ratings than Jeremy Corbyn currently does for 15 months after the 2010 Labour leadership election.”

“Corbyn now has a net negative approval rating even among those who voted Labour in 2015 (-6, down from +27 in November),” said YouGov.

Meanwhile Britain’s Prime Minister and the leader of the Conservative party David Cameron is sitting pretty compared to Corbyn.

“Cameron has a neutral rating among the general public with 47% saying he is doing well and 47% saying he is doing badly, and our most recent voting intention figures have the Conservatives on 41% to Labour’s 30%,” said YouGov. “This lead of 11 is a four point improvement on the general election result.”

This in turn has boosted voting intentions:

Britain’s parliament will decide today whether it will launch a bombing campaign against ISIS in Syria.

Prime Minister David Cameron, who stepped up pressure for air strikes after last month’s Paris attacks, will lead the House of Commons into more than 10 hours of debate on joining the US-led international military action. The debate will start at 11.30 a.m. GMT while the vote on whether Britain will launch air strikes will be at 10 p.m. GMT.

Here are the latest air strike approval numbers within each party, according to YouGov:

Meanwhile, while the public support for a bombing in Syria is sliding, but it is still in the majority:

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