The divide between House and Senate Republicans over how to handle future primaries highlights how intractable the problem of blocking extreme candidates is for Republicans. In Michigan, Tudor Dixon hasn’t ruled out a run for an open Senate seat there after falling to Gov. “You can’t stop people who want to run, it’s a free country,” said Sen. John Cornyn (R-Texas), a former chair of the Senate GOP campaign arm. ), noting that his party needs a “counter” for when House Democrats meddle in GOP primaries. But House Republicans are not planning to aggressively pick primary winners.