A curious coincidence is that the US midterm elections happened one day after the US reimposed its second round of illegal economic sanctions on Iran, with the focus on oil, shipping, and banking, along with some other sectors. Despite all but a handful of governments around the world supporting Iran in this matter (despite apparently two attempted assassinations of opponents of Iran's government in European nations recently) against the US out of a hope to keep Iran following the JCPOA nuclear agreement as it has by all reports been doing, the impact of the midterm elections is probably to reinforce support for Trump's policy, even as mostly he lost support in the election. The reason is that the most important location for serious critics of a president's foreign policy usually come out of the Senate, not the House of Representatives or governors. So, even though the Dems have taken the House and gained governorships, the GOP gaiined in the Senate, and some of the GOPs leaving included the few Trump critics, notably departing Foreign Relations committee Chair, Robert Corker of TN. This is the case, even as those GOP gains may only amount to a net two (Dem Sinema now ahead in AZ) or even only one (Nelson in FL may yet pull it out too).
Yet another reason the gains by Dems will probably not lead to much more pressure on Trump on this is that many Dems at least somewhat support his policy, especially those strongly influenced by the Israeli government. Thus in today's Washington Post, a lead editorial (presumably by neoconnish Fred Hiatt) said there may be reasons for imposing some sanctions because of "malignant" policies by Iran, notably supposedly supplying missiles to the Houthis in Yemen, plus the Syrian government, and Hezbollah in Lebanon (there are doubts on the extent of all this), even as WaPo opposes the US withdrawing from the JCPOA and is highly critical of Saudi Arabia due to the murder of their journalist, Jamal Khashoggi, probably on orders of KSA Crown Prince MbS, a main enemy of Iran. Indeed, members of both parties in the Senate have become unhappy with the Saudi war in Yemen and may move to cut US military support of the Saudi war effort there. But this will probably have little to no effect on the reimposed economic sanctions on Iran.
As it is, the ultimate impact of the new sanctions is quite complicated with various cross-cutting effects that are already damaging the Iranian economy, but may end up having less impact than Trump would like. The most important part of the sanctions involves Iran's oil exports, which US officials claim they would like to see go to zero. Early forecasts had those falling to about a third of the about 2.8 million bpd of a few months ago, which anticipation helped push oil prices up substantially, with Brent crude topping $80 per barrel while West Texas intermediate crude topped $70 per barrel. But the Trump administration has granted temporary waivers to 8 countries allowing them to continue importing Iranian oil for awhile, supposedly to avoid excessive disruption of global markers (while not officially announced, the Japan Times claims the 8 waivered nations are China, India, Japan, South Korea, Taiwan, Turkey, Italy [only EU nation on list]. and UAE [yes, that big anti-Iran oil exporter imports oil from Iran]). As it is, with surging oil inventories in the US, prices have fallen sharply in the last two weeks, with Brent down to nearly $70 and WTI to nearly $60 , with some commenters today claiming that oil is turning into a "bear market." While this clearly allows Iran to export more oil than previously thought for now, the price decline will hurt Iran.
A fundamental clash in this is between governments and the businesses based in their nations. Only a handful of national governments officially support Trump in this policy, basically the odd group of Saudi Arabia, Israel, UAE, Bahrain, and apparently Egypt, with a few others sort of semi-supportive, such as Jordan, if with little enthusiasm. Russia, China, Turkey, and the major EU nations all oppose Trump's policy. While businesses in Russia in particular go along with their government's view, nearly all of those that are reasonably large in the EU nations are obeying the demands of the US government to cut back business relations with Iran, with poster boys for this being Total and Peugeot from France out of fear of losing markets in the US or facing sanctions from the US government. All of this has led to efforts in both China and the EU to set up alternative payment systems to avoid using US dollars and going through US-controlled financial intermediaries, a big conflict over this involving the SWIFT payment system, which the US would like to prevent Iran from using while the major European nations oppose this move by the US. As it is, given the ongoing efforts by they EU nations to help Iran out, it seems especially unwise of Iranian intel agencies to be attempting to assassinate people in France and Denmark as they have reportedly done, albeit unsuccessfully so far.
A final point is that it is extremely unlikely that this policy by Trump will lead to Iranian leaders kowtowing to him and entering into any negotiations. If anything, they might get pushed into pulling out of the JCPOA or create trouble for their enemies in various ways. OTOH, it may be that the sanctions will not lead to as harsh impacts on the Iranian economy as forecast, whether this is due to the Europeans and Chinese setting up alternative payments systems, or due to Iran wriggling out of the sanctions whether due to waivers or through such maneuvers as barter transactions involving oil or the use of "ghost ships" that do not use any radio communications, something reportedly already going on. We shall see how this all turns out, but for now Trump probably has gotten a modest boost of support for his policies within the US as a result of the midterm elections, much as I am not pleased to see this.