Unlike the sanctions that preceded the 2015 nuclear agreement, which were imposed by all world powers—including Russia and China—this time the US stands alone. Moreover, the European Union and the other world powers are making every effort to torpedo the American sanctions. The export of oil and gas is Iran's main source of foreign income, and the loss of even a part of it could be critical, especially in the midst of the economic crisis Tehran is experiencing, which is only getting worse.
The US is hoping the yoke of the sanctions will pose a threat to the ayatollahs regime, intensify the mass protests against the government, or at the very least lead to negotiations over a new nuclear agreement, which will do away with the flaws of the existing deal (that the US has already pulled out of). The new agreement, Washington hopes, will address issues that were left out of the original one, including the testing of long-range missiles that can carry nuclear payloads and Iran's aggression across the Middle East.
The Iranians are very worried by the destructive ramifications of the new sanctions. They therefore hope for a Republican loss in the midterm elections, working under the assumption that if the Democrats manage to regain control of at least one house of Congress, Trump would have a hard time governing and would have to invest a lot more efforts into passing budgets, laws and decisions. If the Democrats gain control of the House of Representatives, the regime in Tehran hopes, they may launch a process to impeach the president, which could, at the very least, hurt his chances to be elected for a second term in 2020.
In any case, the Iranian leadership believes that if the Democrats win the midterm elections, they would limit new possible initiatives Trump might wish to take against the Islamic Republic, and so Tehran would only have to hold on for two years against the sanctions. After that, a Democrat might get elected to the White House and completely change the American attitude towards Iran, returning it to what it was in the Obama era. If the Republicans win and maintain control over both houses of Congress—consequently bolstering Trump ahead of the 2020 presidential elections—Iran would have to turn to other options.
A Democratic win could also harm US-Israel ties. Trump is the most pro-Israeli American president since Ronald Reagan. The Democratic Party, meanwhile, is moving towards the radical left, which will affect the midterms as well. Israel support among Democrats has plummeted over the past decade, which is evident in public opinion polls, the party's platform, and the positions of some of its veteran representatives as well as of those who might join them in the coming election.
The fight between Israel and Iran will move to Washington with the midterm elections. Just as Iran hopes for a Democratic victory, Israel wishes for a Republican win, which will allow Trump to continue his pressure on Iran and his pro-Israel moves. And so, the midterm elections' results could have a significant impact on Israel's security and welfare.
Eytan Gilboa is an expert on the US, the Director of the Center for International Communication and a senior research associate at the BESA Center for Strategic Studies at Bar-Ilan University.