Europe

The electoral system of France was specifically designed this way after the Paris Commune, to prevent communists from ever achieving power:

1. Parliamentary seat elections go for 2 rounds. In the first round, anybody can run. In the second round, only the candidates who achieved a certain % of votes. But in the second round, any of the running candidates can freely drop out of the race. This has been a frequently used tactic over the last century. A district has a communist and a bunch of centrists and right-wingers running. The communist wins the first round of elections. The centrists and right-wingers come together and agree to drop out except one person, who everyone else backs. In the second round, the communist ends up losing. The first round essentially serves as a test run, to see if the communist is a threat, or if the other candidates can have their little fair competition.

2. The president is really more like a king in France. The president gives the order to the parliament to form a government. If he doesn't like the formed government, he can reject it and have them try again. Likewise, he can suggest a government to the parliament (which is what French presidents usually choose to do), and if the parliament doesn't like it, it can reject it. But the thing is, in practice, the parliament needs the president more than the president needs the parliament. So the president is better able to form alliances with different parties, than different parties with each other. Moreover, the centrist-rightist anti-communist coalition applies here as well, so if the president is a communist, the parliament can easily coalesce against him. If the parliament was won by the communists, then most likely the president will still have enough seats in the parliament to block off the communists.

3. The presidential elections work in a similar fashion. Though, that is true for most of Europe, it is still extremely difficult for leftists to win, because of the natural tendency of non-leftist factions in France to band together to save the country from communism.

The only way for the communists to win power in France is to have such overwhelming support as to win both rounds of parliamentary elections, and then get an overwhelming majority in parliament, and then work to maintain their support so they can win the presidential elections as well. If they don't hold both a <50% majority in parliament and the presidency, then their rule shall be hindered at every opportunity.

The left coalition ironically used #1 to beat LePen's party. But because they didn't secure an independent majority of seats, they were doomed. Which is why on the first day after the elections people were saying "The left won the votes, Macron won the elections".

indeed