A prominent neoconservative intellectual and early promoter of the Iraq War is headlining an official campaign fundraiser for Hillary Clinton next month, Foreign Policy has learned. The move signals a shift in the Clinton campaign’s willingness to associate with prominent Republicans and is the latest sign of how far some GOP defectors are willing to go to block a Donald Trump presidency.

Robert Kagan, a senior fellow at the Brookings Institution and a co-founder of the Project for the New American Century, will speak at a Hillary for America fundraiser in Washington’s Logan Circle neighborhood on July 21. According to an invite obtained by FP, the “event will include an off-the-record conversation on America’s continued investment in NATO, key European allies and partners, and the EU.”

Kagan did not immediately respond to a request for comment.

The Clinton campaign has made clear it believes Trump’s high unfavorable ratings and provocative comments have created an opening for her candidacy among traditional GOP voters, and will soon begin actively courting the Republican electorate.