As the M.O.U. crumbles, the price of gas is going back up again. That's where America stands with Donald Trump's on-again/off-again war of choice with Iran. The Memorandum Of Understanding that both sides signed less than a month ago now lies in tatters, Trump just announced that U.S. military ships will re-impose the blockade of Iranian ports, and ships passing through the Strait of Hormuz are under attack again from Iran. All of which has spooked the world's oil market, where prices are (once again) rising fast.

Trump is also threatening to charge a 20 percent tax on all ships passing through the Strait, which would only serve to also increase the price of oil if it ever went into effect. It probably won't, though -- it sounds more like some garden-variety bluster from Trump; just a throwaway line he ejaculates in the midst of the toddler's tantrum he has thrown in response to Iranian provocations. He's talked about levying such a tax or toll before, but never actually done anything about it, and the idea directly contradicts what everyone else in his administration (everyone not currently throwing a tantrum, in other words) has said about it. Here's Marco Rubio, from just a few weeks ago: "No country is allowed to charge tolls or fees on an international waterway. That's existing international law. That's the way it is in international waterways all over the world, and that's the way we expect it'll be here."

As just about everyone commented at the time, the Memorandum Of Understanding reached with Iran was a huge victory for Iran and a huge defeat for the United States. It was supposed to usher in a period where serious talks about the nuclear issue happened within an incredibly short 60-day period, to be followed by some sort of more permanent peace deal signed between the two countries. But the M.O.U. didn't even last a month, much less 60 days.

Iran has successfully changed the focus of the talks that were happening, from any discussion about the nuclear material Iran still possesses to quibbling about what the M.O.U. said about control of the Strait. Iran read the language as giving it full control, while the United States read the language as guaranteeing free and safe passage through the Strait to all ships for at least the 60-day period. Iran is a past master at dragging negotiations out not just over the span of months but of years, so this entire disagreement was entirely predictable. Indeed, many people did predict such a disagreement, when the text of the M.O.U. was finally made public.

All of this takes the world a big step backwards, of course. But the biggest impact here at home could be the effect it has on the American consumer and the American political situation. Because a rise in gas prices right now (with no end in sight) could doom the Republicans' chances in the midterm elections.

Before any of this happened, I made an off-the-cuff prediction. I arbitrarily picked a number and predicted that if the price of gas was still above $3.50 a gallon (the nationwide average price, to be clear) at the end of the summer, then Republicans would be toast in November. I figured that anything below $3.50 could be rationalized by voters as being not that much worse than when Trump took office (when the price per gallon was roughly $3.10) and therefore they could still give the Republicans (and Trump) the benefit of the doubt. However, anything above that line would not be so easily rationalized and voter anger would probably win out.

I have no idea whether my benchmark was realistic or not, but it seemed reasonable to me (in terms of gas prices affecting politics). And I have been watching as prices have indeed come down, because they seemed to be on a trajectory to hit that benchmark perhaps in early August -- which would qualify as "by the end of the summer."

The entire trajectory of gas prices in America has played out since the start of the year, when the saber-rattling over Iran truly began. In January, the price had fallen to $2.75 per gallon -- the first notable decrease in gas prices during Trump's current term of office. This inched up as the saber-rattling continued, and the price was around $2.95 per gallon when the war began.

Once the shooting started, prices skyrocketed at once. This continued until they started to even out in April, when a two-week ceasefire was announced. The price by then had gone over the psychological "four bucks a gallon" barrier and topped out above $4.10 per gallon. It then gradually fell back a bit as people's hopes were raised. But then the U.S. upped the ante by instituting a naval blockade of Iran's ports, and the prices began to climb once again. By early May the price topped out at a whopping $4.57 per gallon -- a full $1.60 in "war taxes" on the American consumer for each and every gallon (the increase since the war began).

Prices then hit a plateau, as the talks between the two countries intensified and the Trump administration kept saying a deal was imminent. The markets reacted optimistically by going down, and by the time the M.O.U. was signed (on June 17th), the price had dropped back down to just below $4.00 per gallon once again. Things were looking better for the Republicans at this point, which was why Trump was so desperate to sign such a flawed M.O.U. in the first place.

After the M.O.U. was signed and ships began to once again safely make it through the Strait, prices continued to fall. But the oil markets began predicting that the talks were in jeopardy about a week ago, and that trend reversed itself. On July 5th the average nationwide price of gas had fallen to $3.72, but within a week had climbed back to $3.85. Today, the price per barrel of oil worldwide shot up by nine percent, which likely means this upward trend at the gas pumps in American is going to continue at least for the foreseeable future.

What this all means for November is still anyone's guess. With Trump in the White House, events happen at a whipsaw pace, so who knows what the situation will be even a few weeks from now? Maybe an updated M.O.U. will be agreed to. Maybe a full-on shooting war will once again be happening. Your guess is as good as mine.

There's a rule of thumb in politics that I relied upon when predicting that arbitrary benchmark. The rule is that whatever the American people feel about the economy at the end of the summer of an election year, they're going to probably feel the same way when they go vote. Even if there's a radical shift (for either the better or the worse), the public's attitude kind of gets set into stone at some point before the election (some put this point at "three months prior" but I used the end of August just to play it safe).

There is still a month and a half before we get to that point. But with the outlook fairly grim in the Strait of Hormuz right now, the Republicans' chances in November are looking pretty dismal. Because nobody who voted for Trump this time around did so thinking, "I bet Trump will hike the price of gas through the roof -- and that'd make America great again!" Well, maybe some oil company executives, but nobody else was thinking along those lines. And if "more Republican control of everything" seems to guarantee more of the same, then the Republicans will be in trouble on Election Day.

At this point, that still seems like a pretty safe prediction to make.

-- Chris Weigant

Follow Chris on Twitter: @ChrisWeigant