The current government, headed by the centrist Kadima party, includes the left-wing Labor party, the Pensioners party and Shas, an ultra-Orthodox Sephardic party. There have been sharp tensions between Livni and the Labor leader, Defence Minister Ehud Barak, but he seems likely to join her to seek to avoid elections that could carry Likud to power.

The Pensioners will pose no difficulties but Shas is more naturally inclined toward Likud, which advocates a tougher approach toward the Palestinians, the ending of peace talks with the Syrians and a solemn vow never to give up sovereignty over any part of Jerusalem to the Palestinians who seek its eastern part as their capital.

Shas, whose members have large families, also wants a big increase in child welfare allowances, which Livni says she opposes.

She could turn to Meretz, which is to the left of Labor. She has also said she would try to attract Likud. But Netanyahu, the Likud leader, said on Wednesday that joining Kadima in a government would be tantamount to joining the board of Lehman Brothers.