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Iran War Cost Hits $37.5 Billion With No End in Sight: How Midterm Odds Are Reacting

Quick Facts at a Glance

• The Iran war has cost $37.5 billion so far, up from a $29 billion estimate just two months ago, and the Pentagon is now asking Congress for $67.1 billion more on top of that.
• A new poll shows the share of Trump’s own MAGA voters who think the war is worth its cost has dropped from about 50% in May to roughly a third today.
• BetOnline’s Balance of Power market prices Democrats as the House favorite in nearly every scenario, while the Senate sits much closer to a true coin flip.

Market Snapshot

Defense Secretary Pete Hegseth told the Senate Appropriations Committee on July 21, 2026 that the war against Iran has cost $37.5 billion to date, and asked lawmakers for $67.1 billion more in emergency funding, according to Military Times’ coverage of the hearing. That’s a sharp jump from the roughly $29 billion figure Hegseth gave lawmakers back in May.

The hearing landed the same week Trump attended the dignified transfer of four more service members killed since he declared the ceasefire over on July 8.

As of July 22, 2026, BetOnline’s Balance of Power market for the 2026 midterms prices it like this:

Outcome	Odds	Implied Probability
Democrats Win Both	+105	48.8%
Democrat House / Republican Senate	+130	43.5%
Republicans Win Both	+400	20.0%
Republican House / Democrat Senate	+3300	2.9%

What Moved the Odds

A rising war bill and mounting casualties are exactly the kind of story that shows up in a president’s own base before it shows up in a betting line. A new Politico poll taken July 13-15 found that the share of Trump’s own MAGA voters who think the war is worth its economic cost has fallen from about 50% in May to just over a third now, a 13-point drop in two months, as reported by Yahoo News.

Nearly 1 in 5 MAGA voters now say the U.S. should end the war regardless of cost, and a majority blame the conflict for rising gas prices, per The Hill’s breakdown of the same poll. An anonymous source close to the White House told Politico that senior staff are “at a maximum level of frustration,” adding that officials now believe “the only way to the victory [Trump] wants is completely politically impossible.”

That matters for a betting market because the president’s party has lost House seats in 18 of the last 20 midterm elections since 1946, a pattern The Conversation traces back through 80 years of election data, and an unpopular, costly war is historically one of the sharpest accelerants of that pattern. It’s no coincidence that Democrats are already priced as the most likely outcome in two of the four scenarios above.

This isn’t just a historical pattern playing out on paper, either. Prediction markets are already showing it in real time: Kalshi’s newly launched Midterms Hub put Republicans’ odds of holding the Senate at just 56% as of July 22, down from 67% back in January, with the site attributing much of that slide to the Iran conflict specifically.

Those are Kalshi and Polymarket numbers rather than BetOnline’s own book, so they won’t match the sportsbook odds dollar-for-dollar, but they track the same underlying sentiment and confirm the Senate is the side of the ledger actually moving right now.

What the Probability Implies

Add up the implied probabilities across all four outcomes and you get about 115%, that gap over 100% is the sportsbook’s built-in hold, roughly 15 cents on the dollar here. It means BetOnline is pricing in a margin the way every book does, so read these numbers as directional rather than exact.

With that in mind, the market is telling you two different things about two different chambers. It’s fairly confident about the House, Democrats show up as the favorite across both winning scenarios, combining for over 92% implied probability. It’s far less confident about the Senate, where a full Republican sweep still sits at 20%, a real, bettable possibility rather than a long shot.

Why This Market Is Different

Unlike a game with a fixed set of rules, this line is reacting to something genuinely unresolved: a war with no clear end date and a funding request that could climb again before November.

Political betting markets like this move on sentiment and news cycles as much as hard data; a single bad news week, more casualties, a cost overrun, or a new poll can shift these numbers well before Election Day itself. That’s different from a sports line that’s mostly locked once the game starts.

What Could Change Next

Watch three things: whether Congress approves the $67.1 billion supplemental request without a fight, whether more casualties or cost figures surface before voters head to the polls, and whether the ceasefire gets renegotiated at all. Any of those could move the House and Senate lines independently.

GamblingNerd Take

The interesting thing here isn’t that a war is unpopular; wars usually are once the bill comes due. It’s that the erosion is happening inside Trump’s own coalition, and that’s the kind of shift that tends to show up in a betting line before it shows up in a campaign ad.

The House number already looks like it’s absorbed most of that story. At a combined 92% implied probability for a Democratic House, there’s not much room left for that price to move. The Senate hasn’t caught up yet, and that’s where I’d actually put attention: a 20% chance of a full Republican sweep looks generous if the MAGA-base erosion in this poll keeps compounding month over month.

If you’re weighing a bet here, don’t put money on the House markets expecting a discount; that price already reflects the bad news. Instead, watch the Senate-specific line specifically after the next casualty report, funding vote, or polling update, since that’s the side of the ledger still catching up to the story.

A line that hasn’t moved yet after a fresh round of bad news for the GOP is exactly the kind of gap worth acting on.