We may be living in the “Year of the Mega Deal,” but the latest announced merger may signal an era is coming to an end.

Bayer’s (OTC: BAYRY) proposed takeover of Monsanto (NYSE: MON), is a transaction valued at $66 billion including debt, making it the biggest deal of the year and the largest transaction ever by a German buyer. It follows other mega deals this year, including Syngenta being acquired by China National Chemical for $48 billion and Abbott Laboratories picking up St. Jude Medical for $30.6 billion.

Mergers and acquisitions have been on fire, with last year global deal’s hitting $5 trillion. This year isn’t likely to come anywhere near that, with total global M&A valued at just $1.71 trillion in the first half of 2016.

What makes the possible Bayer/Monsanto deal interesting isn’t just its size. It’s what it may spell for the merger wave.

About the deal: While Bayer is probably best known for its namesake aspirin and Alka-Seltzer, it does have a crop sciences division which mostly makes weed and bug killers. So the merger would create one of the world’s largest agribusinesses by marrying Bayer’s crop sciences operations with Monsanto’s seed and chemical business.

The deal makes solid strategic sense for the companies; there has been a wave of agribusiness deals recently that is making the market increasingly competitive. Plus, with two companies as large as they are it takes a lot of growth to drive earnings higher. They pick up instant market share by hitching their horses together, plus they estimate they can cut more than $1 billion in costs.

The real question is if the deal can actually get done. I’m not so sure it can, at least not without significant divestures. For one thing, farmers will cry foul. Input costs for farmers – seeds, fertilizers, pesticides and herbicides – have risen by double digits over the last several years, and many farmers believe industry consolidation is a big reason why. And there are big mergers in the works involving DuPont and Dow Chemical, and Agrium and Potash Corp.

While Bayer and Monsanto say they expect the deal to close by the end of next year, they’ve also said they’ll need to get antirust approvals in 30 different global jurisdictions, including in the United States. Our own antitrust cops have been blocking deals at a record rate recently, and more than $600 billion worth of global M&A deals were scuttled in the first half of the year, mostly due to regulatory intervention.

Here in the U.S., farmers are a powerful political constituency. For proof you need look no further than the Farm Bills passed by Congress. Back in March, the Congressional Budget Office released an updated spending report that included the 2014 Farm Bill, which alone would spend $956 billion over the next ten years.

Before I get any angry letters, I’m not speaking ill of farmers. I’m just saying that they’re well organized and already unhappy, so they’ll be applying a lot of pressure to get this deal scuttled.  And we have an election coming up in November, the results of which could affect the odds of the deal getting done. Deals of this size take time for regulators to evaluate and there’s no way that process will be compete before the new administration takes office.

I’m betting that this deal is going to wither on the vine and I’d look for the pace of these mega deals to slow down.