Political groups aligned with Sen. Mitch McConnell are amassing a $190 million war chest as the Senate majority leader and allies warn Republican donors, amid an impeachment inquiry into President Trump, that a GOP Senate is the only reliable defense against Democrats sweeping in 2020.

Senate Leadership Fund and One Nation have emerged as the primary source of outside air cover for Senate Republicans. The super PAC and its affiliated nonprofit are central to McConnell’s strategy to protect his three-seat majority against the specter of impeachment and insulate vulnerable Republicans from Democratic challenges. And, in conversations with GOP contributors about the two groups, McConnell and his boosters are pitching the Senate as the party’s insurance policy for a Trump defeat.