With the announcement of the United States Treasury taking steps to curb inversion deals that will allow companies to avoid the high U.S. taxes, shares of AstraZeneca plc (ADR) (NYSE: AZN) and Shire PLC (ADR)(NASDAQ: SHPG) have dropped drastically.

With the Treasury department intervening, agreed deals like AbbVie Inc. (NYSE: ABBV) buying Shire for $55 billion and the deal between Pfizer Inc. (NYSE: PFE) and AstraZeneca are now in jeopardy. Both AstraZeneca and Shire combined have lost $8 billion in market value since President Obama shed light on the negative effects of companies doing tax inversion deals.

Many investors had expected the Obama administration to step in, and they were correct. The administration started mentioning how companies that are reincorporating should be to blame for America’s economy. The tax inversion deals are now the top priority for Democrats all over the country, while the Republicans believe that other issues are more important at the moment.

Navid Malik, head of Life Science research at Cenkos Securities said that with the administrations putting a black cloud on those companies who are trying to dodge the high American tax rate. “Inversion deals now are clearly going to be very difficult to pull off,” said Malik.

The Treasury is also limiting levels of ownership that the former U.S. owners have once they reincorporate elsewhere. The issue now is finding a way to help companies incorporating in America and doing it while paying lower tax rates. Look at tax inversions to be an important topic for both parties in upcoming elections.