I believe that the Jews will believe on Christ without seeing Him. But they will see His Resurrection Power, in the middle of the Great Tribulation, when He raises His Two Witnesses from the dead before them. And they watch them ascend, as Christ did. The Jews will then believe that the Testimony and Prophecies the Two Witnesses made are true. And they will then know that the Antichrist is against them. They will then flee Jerusalem, as prophecied, and be sheltered by God for the second half of the Great Tribulation. The 144,000 that were sealed, shall be spread out upon the earth. When the world is tormented by the scorpion locusts for 5 months, and they seek death and cannot find it, the 144,000 are not harmed by the scorpion locusts. Logically, those who were tormented, would like either seek to obtain the blessings that the 144,000 are under, or despise them in envy. I would suspect both. There must be widespread salvation of enough Gentiles during the second half of the Tribulation, for the nations to repopulate the earth during Christ's thousand year reign. Those 144,000 sealed Jews shall lead many to Christ.