In the parliamentary systems of our allies, such as Canada or the United Kingdom, a vote for a candidate at any level is almost always a vote for a governing party and its leadership: The party that gains the most legislative seats gets to form a government and choose a prime minister.

By contrast, one of the great virtues of the American system of separated powers is that voters, usually, can ignore party affiliation if they feel a candidate is worth their support. Our model forces the legislative and executive branches to seek separate mandates from the electorate. In our system, voters can separate the party from its leader. They can split their tickets regionally, nationally and by party. They can even vote for divided government, and choose to place the executive and legislative power in opposing hands.

For now, however, those days are over — at least for the Republican Party. Rather than acting like a national party, entrusted with separate but coequal branches of government, the GOP at every level and in every state has been captured by the personality cult that has congealed around President Trump, and it is now operating like a parliamentary party, utterly submissive to its erratic but powerful prime minister, Trump. Republican elected officials, from Congress to the state houses, have chosen to become little more than enablers for an out of control executive branch.

The only way to put a stop to this is to vote against the GOP in every race, at every level in 2018. It’s tough medicine. But as someone who’s voted Republican for nearly 40 years, who favors limited government and public integrity, and who believes America still needs a credible, responsible center-right party, I see no alternative.

Normally our system tolerates dissent, and such a choice wouldn’t be necessary. Voters could support politicians who would stand in opposition to their own leadership. In the 1970s, for example, President Jimmy Carter faced a rebellion among his own Democrats that led to an actual primary challenge on the left from Sen. Ted Kennedy. Carter faced none of the scandals plaguing Trump, but was seen as ineffective both domestically and abroad, and many Democrats soon had buyer’s remorse over the leader they’d chosen in 1976. In 1980, a voter could still be a Democrat and oppose Carter, because Carter did not rule the party. He was rightly seen as the temporary resident of the White House. ...