The decline in support for the Conservatives has coincided with an unexpectedly strong performance from Corbyn and a surprise announcement by May in which she suggested elderly voters would need to pay more for social care.
"A Tory manifesto with no 'good news', unlike Labour's long, popular if expensive shopping list, and a better-than-expected campaign performance by Corbyn, allowed Labour to close the gap in the opinion polls, albeit from a low base," Eurasia's Rahman said.
The prime minister later backtracked over the social care plans, which critics labeled the "dementia tax", as support deteriorated among wealthy homeowners. The upset caused among a core source of support for the Conservatives appeared to prompt May's political U-turn, although she has repeatedly insisted "nothing has changed."
Conservative candidates told the Huffington Post last week the party deserved to lose the election given the way the party's campaign had been negotiated to date. One Conservative candidate, which the media outlet did not name, said they were pretty "f-----d off" with the prime minister for shattering confidence in the parliamentary party.
"Jeremy Corbyn is running a good campaign but beyond anything else, he's a beneficiary of a truly awful Conservative campaign," Tom Baldwin, former director of communications to ex-Labour leader Ed Miliband, told BBC Newsnight last week.
"I've never seen anything like it — the prime minister is disintegrating in front of the public, she's gone from basing her entire campaign around her personality to her brand being junked within three weeks," Baldwin added.
Pollsters have projected a vast range of outcomes for Thursday's vote, ranging from a landslide majority of well over 100 seats to a YouGov prediction that forecast May would win with 305 seats, slightly less than the 326 seats required for a majority in the 650-seat parliament.
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