U.S. political strategist Jim Messina | Mandel Ngan/AFP/Getty Jim Messina to advise David Cameron’s EU referendum campaign

U.S. political strategist Jim Messina has signed on as “senior strategic adviser” for David Cameron’s campaign to keep Britain in the EU — effective now.

“Given these challenging economic times, the very last thing we should do is risk the U.K. and EU economies with this risky [Brexit] move,” Messina, who managed Barack Obama’s 2012 reelection campaign, told POLITICO in an email.

The former White House deputy chief of staff won’t run the “In” campaign day-to-day but will be “heavily involved” in strategy ahead of the June 23 Brexit referendum, he said. Tara Corrigan, another Obama campaign veteran, will be working with Cameron’s team daily from London.

Messina previously advised Cameron's successful campaign in the U.K. general election in May 2015.