Ehud Olmert's final hour as Prime Minister is getting a lot closer.

Less than a week after President George W. Bush visited Israel and pressed for Israeli politicians to keep Olmert afloat, Avigdor Liberman, the head of the Russian-speaking party Israel Beiteynu (Israel Our Home), abandoned Olmert's ship.

Taking 11 Knesset seats with him, Lieberman shrunk Olmert's coalition from a respectable 78 down to 67, with 11 seats of the Sephardi Orthodox Shas Party still at stake. Ovadiya Yossef, former Chief Sephardi Rabbi of Israel and the influential spiritual leader of Shas, has threatened to bring down Olmert's coalition if it pursues talks on dividing Jerusalem.

There was a deeply personal aspect to Lieberman's frustration and departure. Hounded by a lengthy, and so far futile, police investigation, Lieberman failed to make his boss, Olmert, close the file. In fact, Olmert himself has been the target of at least three criminal probes.

Lieberman, previously a key ally and chief of staff of former Prime Minister Bibi Netanyahu, was Olmert's political enforcer. Though to Olmert's political right, he remained in Olmert's Cabinet because of his dislike of Netanyahu and fear of the new Russian political party called Tsedek Hevrati (Social Justice), headed by Arkady Gaidamak, a billionaire businessman with interests from Africa to Siberia.

On Thursday, the day Lieberman resigned, Israeli police pulled his daughter Michal in for an interrogation about alleged financial irregularities and corruption connected to her father. Police alleged that Lieberman took bribes from the same businessmen who financed the Sharon family, another target of extensive bribery investigations, and that Michal opened companies which facilitated these dubious transactions.

Olmert now will depend on his ability to replace Israel Beiteynu with two diametrically opposed smaller parties: the ultra-Orthodox United Torah Judaism (UTJ) and the leftist, secularist Meretz. However, both of these groups are split as to whether to support the embattled Prime Minister.

The UTJ is concerned about Jerusalem and cuts in child subsidies. (Ultra-Orthodox families are staunchly against birth control, and usually have numerous off-spring). Ultra-Orthodox Jews are generally viewed as somewhat more dovish and do not, as a rule, serve in the Israeli military. Nevertheless, UTJ's Yaakov Litzman, chairman of the Knesset Finance Committee, has expressed concerns about Olmert's diplomacy, while his colleague Abraham Ravitz supports joining the coalition.

Meretz, headed by the former Justice Minister Yossi Beilin (a protégé of President Shimon Peres), has an issue with Olmert's hasty decision last year to go to war with Hezbollah. The group also knows that propping Olmert up now, on the eve of the Winograd Commission's final report, may be counterproductive. The Commission is due to present its conclusions concerning the conduct of the war on January 30^th, and the results are likely to be devastating for Olmert.

Meretz wants to appear anti-war and pro-rule of law. Olmert's lack of popularity could hurt them if they jump on his wagon now. Meretz is also anti-religious, so voting to give more money to the likes of Shas and United Torah may not sit well with its supporters.

But Olmert's troubles don't end with the smaller parties. Discontent is brewing within his own party, Kadima (Forward). Former Chief of Staff of the military, Lt.-Gen. (Ret.) Shaul Mofaz, and Foreign Minister and ex-Mossad agent Tsipi Livni are circling, ready to pounce on the party leader when the Winograd Report is published. Recently, both publicly called for Olmert to resign, and Mofaz went on record saying that he will not let Livni take over the party without a fight.

Even bigger trouble is Olmert's own Defense Minister: Labor Party leader Ehud Barak. The former Prime Minister, who led the failed negotiations with Yasir Arafat, is preparing his "second coming" to the Prime Ministerial post-after Olmert is dispatched.

Barak is trying to build on his image as "Mr. Security." He is an overachiever: Israel's most highly decorated soldier, and a former Chief of Staff, Defense Minister and Prime Minister. Olmert cannot afford to look weak if he wants to remain Prime Minister, especially as Bibi Netanyahu has introduced a no-confidence vote in the Knesset.

Ironically, Hamas is playing into Netanyahu's hands by firing 30-50 Qassam rockets a day on Sderot and other Israeli towns. Barak and Olmert may be forced to launch a land invasion of Gaza in response. So far, a number of leading Palestinian Islamic Jihad (PIJ) militants have been killed, as well as Hamas leader Mohammad Zahar's son. To distract attention from the Winograd Commission report, Olmert may actually prefer to go for an invasion, rather than face the "inconvenient truth" of seeing himself portrayed the most inept Israeli wartime leader in its 60-year existence.

The security challenges do not end with Gaza. Recently, an Israeli Army checkpoint discovered 6.5 tons of a bomb-making chemical, potassium nitrate, hidden in bags of sugar disguised as humanitarian aid en route to Gaza from the West Bank.

And on Thursday Jan. 16^th, the Israeli Shin Beth security services and the military discovered a Palestinian Islamic Jihad (PIJ) cell--along with a sophisticated explosives lab--in the village of Batir near the Green Line. The PIJ planned to bomb the busy Tel-Aviv-Jerusalem railroad, civilian cars, buses, and the neighboring Jewish villages.

As the security situation grows increasingly tense, the sand in Olmert's coalition hourglass may be running out. Yet, Olmert has proven to be a Teflon-coated political survivor in the past and may yet last several more months. But when the history of his prime ministership is written, Avigdor Lieberman's exit will be recorded as the beginning of the end. Moreover, it is likely that the early elections to the Israeli Knesset may happen this year.

Ariel Cohen is senior research fellow at the Heritage Foundation and senior adviser to the U.S.-Ukraine Business Council.