LONDON -- The three contenders to succeed Prime Minister Margaret Thatcher all claimed yesterday that they could beat the opposition Labor Party in the next general election.
Their ability to ensure a fourth Conservative term in office is crucial to the self-survival instincts of the 372 members of Parliament who will vote tomorrow for a new leader.
Under the increasingly unpopular leadership of Mrs. Thatcher, Labor had held a consistent double-digit lead in the polls throughout the year. But her resignation reversed that, with opinion polls yesterday saying that any of the Conservative leadership contenders could beat Labor. The next general election must be held by the summer of 1992.
The challenger best positioned to reverse Labor's prospects of power was identified in the polls as Michael Heseltine, the former defense minister who forced Mrs. Thatcher's resignation last week.
Chancellor of the Exchequer John Major and Foreign Secretary Douglas Hurd, who are also seeking to replace her in tomorrow's vote, were judged to have smaller winning edges over Labor.
"What the Conservative Party understands above all else is unity matters, and we have got to be united to prevent the occurrence of the ultimate disaster, which would be the election of a Labor government," Mr. Heseltine, 57, said on ITV.
Mr. Major, 47, reputed to be Mrs. Thatcher's own choice as her successor, stressed the necessity of continuity of the past 11 1/2 years. "The Conservative Party is united on the fact that we need to build on what has been achieved," he said.
Mr. Hurd, 60, who would have the smallest winning margin over Labor according to the polls, said he was best able to heal the political wounds left by the Thatcher era.