Few American presidents enjoyed the kind of popular appeal that Theodore Roosevelt, a Republican, had during his life. People were heartbroken when he chose not to run again in 1908. But after he changed his mind four years later, the Republican Party came down on the side of his successor, President William Howard Taft. Roosevelt ran as a third party candidate on his “Bull Moose” party ticket and split the Republican vote. Democrat Woodrow Wilson was the beneficiary, with Roosevelt coming in second place, accessorily becoming the first person in U.S. history to run on a third-party ticket and come in one of the top two spots.

>> Read more: If there's one conclusion from the Israeli election results, this is it | Analysis

Sometimes it is easy to forget that no law in the United States requires the government to be controlled by one of the two major parties. The founding fathers built a complex system of government, sophisticated and, on the whole, conservative. It does not promote rapid changes, quite the opposite: The system of checks and balances pushes politics toward consensus. The American public chooses its representatives – congressmen, senators and the president – on an individual basis, and not as part of a party. Every race is between two candidates and the winner takes all, so each bloc comes together in a natural way to form a cohesive party with an agreed-upon candidate.

The system in the United States viciously punishes any bloc that puts forward more than one candidate. As a result, party primaries replicate the dynamic of coalition negotiations, with contenders forced to woo every section of the bloc. Eventually, the chosen candidate benefits from the united, wide-ranging support in their political camp.

The Israeli system, in comparison, rewards splits and divisions. Because the prime minister is dependent on the constant support of at least 61 Knesset members, the margins often have more power than the center. The present desire on both the left and the right to merge into large camps is an interesting development, although it is doomed to fail without a radical change in the electoral system. Even if all parties on the left had come together under a single open and democratic umbrella offering a range of opinions and voices from Benny Gantz through to Esawi Freige – it still would not have survived. With Benjamin Netanyahu in power, or without, shaky governments that depend on the votes of just a few MKs to stay in power remains the reality in Israel.

The entry of the Labor party, headed at the time by Ehud Barak, into Netanyahu’s government 10 years ago was a reality test. Labor won only 13 Knesset seats but still received five ministerial portfolios, including the major defense post. The differences of opinion with Likud and the rest of the coalition partners were quickly felt, and eight of the 13 MKs chose to quit the government. Barak split from Labor, but as the head of a party with only five MKs he was not punished – instead, he kept the important ministries. Netanyahu had no choice, because without Barak and his loyalists he would have headed a dangerous coalition of only 61 MKs.

Turning the left-wing bloc into one large party is a nice thought to ponder, but it has no basis in reality. Even if the left manages to come together as a single unit, there will still be parliamentarians tempted to cross the lines, in 2009 Barak fashion, to be a minister and receive various honors, maybe even for ideological reasons. Unlike the United States, Israel has no formal or informal punishment for those who want to leave their parties and go off independently. Barak is not the only proof of this: Avigdor Lieberman is the perfect example of it on the right.

In the United States, similar splits have been a disaster for both sides. In 1992, the independent candidate Ross Perot divided the right-wing vote and gifted Bill Clinton a surprise victory over incumbent President George H.W. Bush. In 2000, it was the Green Party's Ralph Nader who captured two percent of the vote, shifting the balance in favor of the Republican candidate, George W. Bush. Perot and Nader have become ingrained in American memory as the ones who ruined the chances of their political blocs, and gave the victory to the other side. They act as a powerful deterrent for every politician who considers the option of going solo.

Ralph Waldo Emerson described the political system of his day, 180 years ago, as one in which the engagement with the party bureaucracies distorts the greater truth: “The two parties which divide the State, the party of Conservatism and that of Innovation are very old, and have disputed the possession of the world ever since it was made.”

The lesson for the Israeli left is that not everything can be left to these magical “mergers” that have lately been all the rage. Salvation cannot be left to mere technicalities. The existing system of government requires political parties to create platforms based on core ideas. Only then can cooperation between different parties exist. Israel might want to follow the American model, and build coalitions before the elections, not after.