May's lead narrows on eve of UK general election Polls suggest a much tighter race than predicted when the election was called.

 LONDON -- When U.K. Prime Minister Theresa May called a snap general election in April, polls suggested a big lead for her Conservative Party over rival Labour Party. But now, one day before British voters cast their ballots, polls predict a much tighter race.

In recent weeks, May has lost popularity over some of her social care policies, including a so-called “dementia tax,” which would make pensioners pay a bigger part of the cost of their care.

“One is that there was a terrible reaction to the Conservative policy proposals on social care,” Stephen Fisher, associate professor in political sociology at the University of Oxford, told ABC News. “Around the same time Theresa May’s performances in press conferences and her campaigning style were not as polished as Jeremy Corbyn’s so people warmed a lot to Jeremy Corbyn and the Labour party and were less impressed with the Conservatives.“

An average of opinions polls published by the Economist shows the Conservative Party leading with 44 percent of voters' support to Labour's 36 percent, but support for the Labour Party has been rising steadily since April -- by some 10 points, according to the average.

Some polls suggest such a close election that a hung parliament becomes a possibility -- meaning that no single political party has an absolute majority, which would raise questions about who will govern the U.K. in the future, Fisher said.

Recently, May's campaign has also been affected by attacks on London Bridge and in Manchester.

“There is no doubt that the Conservative Party failed to match the initial expectations of a convincing landslide,” Matthew Goodwin, professor of politics and international relations at the University of Kent, England, told ABC News via email. “The campaign period has seen considerable volatility, including two terrorist attacks, a u-turn on the major policy issue of social care and an upsurge of public support -- at least in the polls -- for Jeremy Corbyn and the Labour Party.“

He added that the Conservative Party has nonetheless maintained a share of the national vote in the polls of above 40 percent, a strong position -- and that most opinion polls put the Conservatives ahead of the other parties.

“Most of the ‘fundamentals’ in this campaign also favor Theresa May and her party, which is the most trusted party on Brexit, immigration, the economy and also security issues that have gained importance in recent years,” he said.

A very personalized, almost presidential style of campaigning has contributed to the Conservative party’s apparent loss of support, said Mark Goodwin, lecturer at the department of political science and international studies at the University of Birmingham in England.

“Theresa May has been in British politics for quite a long time, but she is not somebody with a huge media profile or who is associated with particular policy positions,” he told ABC News. “She seems to have found it very difficult to kind of do the baby-kissing part of campaigning.”

A week ago, May’s political rivals criticized her for staying away from a televised election debate while her main opponent, Jeremy Corbyn, leader of the Labour party, participated in the debate.

“It’s a relative novel thing in British politics, but if you’re about leadership perhaps you turn up to these things,” he said. ”The idea that it was in some sense beneath Theresa May to appear alongside these minor parties in the televised debate, that she’s someone above the pettiness and inter-party conflict of these debates was possibly the strategy that backfired somewhat.”

It’s difficult to predict what the election result will be because of a number of high-profile polling misses in British politics lately, he said -- including in connection with the British referendum in June last year when a majority voted to leave the European Union.

“So you have to be a little more tentative than in the past,” he said, adding that polls suggest that the Conservatives will win, but that Labour has been doing much better in the past few weeks, especially compared to the early days of the campaign, when polls suggested that the Conservative Party was headed to a landslide victory while Labour could perhaps be wiped out.

“That seems less and less likely,” he said.