On Tuesday night, Representative Kerry Bentivolio of Michigan became the third incumbent to lose his House seat in this year’s primaries, but over in the Senate, incumbents kept up their winning streak. Sitting senators have already beaten primary challengers in Texas, Kentucky, South Carolina, and Mississippi, and now Senator Pat Roberts of Kansas has done the same. With 95 percent of precincts reporting, the three-term Republican was leading tea-party challenger Milton Wolf, 48 percent to 41 percent. Wolf, a radiologist and second cousin of President Obama, campaigned as a staunch conservative devoted to undoing Obamacare, but he was hurt by revelations that he posted patients’ X-rays on Facebook. Ultimately, the federal government just wasn’t big enough for two members of the Obama family — or rather, it wasn’t big enough for the president and a guy who makes macabre jokes about his patients online.