But critics fear that the tabloid spells doom for a free media in Israel. They say the newspaper has a clear political agenda to support Mr Netanyahu. And the bottomless pockets of Mr Adelson, 76, presents a threat to the survival of his competitors and the wider issue of free speech that thrives in a diverse media. It is a criticism firmly rejected by Mr Adelson, a self-professed Zionist opposed to the two-state solution who reportedly once accused the owner of Ma'ariv, a rival title, of not being patriotic enough.
He is certainly a fascinating figure. Mr Adelson, described by one U.S. publication as "the richest man you never heard of", built a gambling empire that propelled him into the ranks of the top-three wealthiest men in America.
With a string of lawsuits behind him, Mr Adelson's peers describe him as an aggressive opponent, who is not afraid to play nasty. He has given hundreds of millions of dollars to right-wing and Zionist causes, many of them in Israel, and was a generous donor to US President George W Bush's re-election campaign for 2004.
"Everybody thinks I started the newspaper purely to benefit Bibi [Netanyahu]. Nothing could be further from the truth," Mr Adelson once told the Jewish Telegraph Agency. "I started the newspaper to give Israel, Israelis, a fair and balanced view of the news and the views. That's all. It is not a 'Bibiton.'"
Israel Hayom has taken a marginal lead of 0.3 per centage points of total readership over the popular daily Yedioth Aharonot, according to TGI Research, which conducts a biannual survey of newspaper readership. The rise falls within the survey's margin of error, but puts the freesheet on a par with Yedioth for the first time.
Israel Hayom is now read by some 35 per cent of Israelis, 10 percent up on a survey six months ago. Ma'ariv, another popular Israeli tabloid, trails in third with 12.5 per cent, while Haaretz, a liberal broadsheet, stands at 6.4 per cent.
The development underscores the successful model of a free paper and marks a radical shift in Israel's newspaper industry, which for decades has been dominated by just three titles. "This is endless capital with a political agenda," said Ben-Dror Yemini, a columnist with Ma'ariv. "We have no idea how to deal with it."
Since its establishment, the paper has slavishly supported and promoted Mr Netanyahu, media experts say, while it was fiercely critical of his predecessor, Ehud Olmert, who was toppled over corruption charges. "If you follow how they edit it, when they are pro-Netanyahu and when they hide information on Netanyahu, you realise very quickly that they are a pro-Netanyahu paper," said Uri Benziman, editor of Seventh Eye, a media watchdog affiliated to the Israel Democracy Institute. The newspaper refused to respond to the criticisms, saying only that "the [survey's] results speak for themselves".
Israel Hayom's early success provoked a storm of reaction in Israel, chiefly from its paying competitors Yedioth and Ma'ariv, both of which found themselves vulnerable to the circulation war.
Lobbied by newspaper chiefs, centrist politicians tried to get a Bill through parliament that would outlaw foreign ownership of an Israeli newspaper, citing fears that an outsider could influence domestic opinion. In another legislative attack, parliamentarians sought, again unsuccessfully, to limit the distribution of free newspapers.
Even today, though, it is difficult to measure Israel Hayom's influence. Every morning, an army of uniformed workers takes up position on major pedestrian streets, traffic intersections and train stations to hand out the freesheet.
Israel Hayom aspires to be on a par with its competitors. It is long at 64 pages or so, and closely imitates its main rivals. It uses scores of well-known commentators, some of them from the leftist camp.
But its impact on opinion is still negligible, experts say. It does not break stories, its columns do not shape opinion in the way that its competitors do. "I think its main success is because it's free," Mr Benziman said. "If it had to compete in a real market, it wouldn't do so well."
Nevertheless, the fact that it is so widely read reflects a growing right-wing phenomenon in Israel, influenced by a wave of nationalist immigrants from the former Soviet Union in the past two decades.
There is also a backlash against the Second Intifida, the Palestinian mass uprising characterised by frequent suicide bombings. At the elections in early 2009, even though centrist Kadima won the most seats, it was a victory for the right-wing which formed a coalition government with Mr Netanyahu at its head.
And in a survey earlier this year, a majority of Israelis said there was too much freedom of expression in Israel, and that journalists critical of the defence establishment ought to be punished for their criticisms.
Liberals seized on the findings with horror, but the poll nevertheless supports a growing perception within Israel that the left-wing media, such as the liberal Haaretz newspaper, are critical of the government to the extent that it is harmful to the state. Mr Adelson's paper is able to capitalise on that fear, playing on "patriotic emotions," said Mr Benziman. Those emotions were being har nessed yesterday, as a congratulatory editorial in the paper intoned: "Israel Hayom loves the State of Israel; therefore, Israeli people love Israel Hayom."
As the title pushes into the lead in the circulation wars, some commentators now fear that the debate has run its course.
"What does it mean for Israeli democracy? What does it mean for free speech? I don't have a good answer. Because it's becoming the biggest newspaper, politicians are becoming afraid to speak," said Ma'ariv's Mr Yemini. "We have to talk about it, because I don't want to be swallowed up."
