ST. PAUL — Years before Burger King sized up a Canadian headquarters in a hunt for lower taxes, Republican U.S. Senate candidate Mike McFadden’s investment firm was involved in a merger that moved an American pharmaceutical company to Ireland and significantly dropped its tax rate.

McFadden’s Minnesota-based firm made more than $11 million, according to public filings.

The 2012 deal came at the foot of a recent wave of so-called tax inversions in which U.S. companies merge with a foreign partner and reincorporate abroad to generate tax savings. With such deals increasingly grabbing headlines, it could become a flashpoint in the Minnesota race as McFadden tries to unseat Democratic U.S. Sen. Al Franken.

Inversions are legal, but politicians — including McFadden — are calling for a clampdown. He has described it as a “tragedy” when the U.S. loses tax revenues if a company moves overseas, such as Minnesota-based Medtronic. The company also is eyeing Ireland, where the corporate tax rate is 12.5 percent compared with 35 percent in the U.S., while Burger King announced this week it planned to acquire Canadian coffee chain Tim Horton’s and shift its tax residence north.

In an interview Friday with The Associated Press, McFadden distanced himself from the 2012 deal that took Jazz Pharmaceuticals abroad; he was CEO of Lazard Middle Market at the time. McFadden portrayed the tax inversion as a one-sided business maneuver driven by Jazz and its financial adviser — not the Irish drugmaker Azur Pharma, which his firm represented.