Prime Minister David Cameron during an election campaign stop at Harris & Hetherington Livestock Mart in Carlisle, Britain, on the eve of the election. (EPA)

As voters around Britain cast their ballots, a majority already believe that David Cameron will again be prime minister when the next government is formed, according to a large-scale poll conducted by SurveyMonkey.

Although neither main party is likely to win a majority of seats in Parliament today, 58 percent of voters predict that Cameron will prevail in the post-election maneuvering to assemble enough seats to remain in power. Thirty-five percent disagree.

The prediction of the 58 percent is hardly an endorsement of the job Cameron and his Conservative Party have done over the past five years. A majority, 54 percent, say they are not satisfied with his performance, while just 45 percent say they are.

But Cameron is buoyed by perceptions that the economy is on the mend. Half of all voters say the economy has been clearly improving over the past year, while only 29 percent say things have gotten worse.

Cameron’s final appeal to voters has been strongly focused on the improvements in the economy and a plea to let his party finish the job. Labor leader Ed Miliband, in contrast, has argued that the policies of the Conservative-Liberal Democrat coalition government have been harmful to working families and that a change of direction is badly needed.

When voters were asked which party they planned to support, 34 percent said Conservative and 28 percent said Labor. The U.K. Independence Party was running third with 13 percent. Most pre-election polls have shown a virtual tie between Labor and Conservatives.

With the rest of the vote splintered, the two main parties will be scrambling to assemble alliances, formal or not, to claim power.

According to the SurveyMonkey data, which includes online interviews with more than 18,000 voters, Labor could be the biggest beneficiary of last-minute vote switches. More than four in 10 voters who indicated they might back either the Liberal Democrats or the Green Party said they might change their mind when casting their ballots.

Labor has also sought to peel away supporters from the Scottish National Party, which is on track to decimate Labor’s strength in Scotland. But those SNP voters are highly enthusiastic and not likely to change their minds.

Among the issues driving voters’ decisions, the economy sits on top, followed by three other sometimes-contentious issues: immigration, inequality and health care. Sixty-three percent of those who cite the economy as their main issue support the Conservatives, while 15 percent do not. Labor leads by wide margins among those who say health care or inequality are their big issues. Conservatives and the UKIP are the two favorites among those who name immigration as their top priority.

Labour leader Ed Miliband smiled for the cameras as he arrived to cast his vote in Britain’s election. Independence Party leader Nigel Farage and Green Party leader Natalie Bennett also turned out to vote. (Reuters)

In a related poll, SurveyMonkey also tested the reaction to various possible coalitions in a new government among those who say they will vote for either of the two main parties.

The Liberal Democrats were seen by far as the most acceptable partner in a future government, whether in coalition or a less formal alliance. Overall, three in four say they would find a government that included the Liberal Democrats acceptable, with support somewhat greater among Conservative voters than among Labor voters.

Miliband and Labor have been sensitive to the opposition in other parts of the country to an alliance with the SNP, which wants to take Scotland out of the United Kingdom. The Labor leader has repeatedly ruled out a coalition or even any “deal” with the SNP, though there seems to be no way for Labor to form a government without the votes of SNP elected officials.

The SurveyMonkey findings showed that among Labor supporters, 57 percent say they would find such an alliance acceptable and 43 percent say they would not. A quarter say they would find it “completely unacceptable.”

Those surveyed had no greater overall appetite for a government dependent on the support of UKIP, with just 31 percent saying such an outcome would be acceptable. Labor voters were overwhelmingly opposed. Not quite half of Conservatives said they saw this as acceptable, while a slight majority opposed it. Although UKIP is polling above 10 percent, it is projected to win only a few seats.

This survey is a continuation of SurveyMonkey’s effort to transform the way political surveys are conducted and comes after experiments in the 2014 U.S. midterm elections.

The results are based on a survey conducted April 30 to May 6 among more than 18,000 voters. The respondents were selected after answering one of the nearly 3 million user-created surveys running each day on the SurveyMonkey platform.

Because the survey is not a random sample of the population, no margin of sampling error can be calculated describing how far results might differ from the overall population.

For more background on the 2014 surveys, see this and this.

Read more:

7 ways the British elections could change Britain

11 weird memes that help explain the British election

In British election campaign, the center cannot hold

Today's coverage from Post correspondents around the world