Republicans have lost the popular vote for president in five of the past six elections. (Rick Wilking/Reuters)

The question that will be front and center at Thursday’s Republican presidential debate is who will lead the party in 2016. As important will be: What kind of party will the GOP nominee end up leading?

For Republicans this is a moment for optimism, but it’s also a time for realism.

On the positive side, they control Congress and enjoy political dominance in the states. Their 17-candidate presidential field, with exceptions, is better than four years ago, stocked with talent and plausible party standard bearers. And Hillary Rodham Clinton looks more vulnerable today than she did at the start of the year.

But that is only part of the equation. The GOP nomination contest has become a circus, currently thanks to Donald Trump. Since last November’s midterm election victories, the party’s image has deteriorated, as has the percentage of Americans who call themselves Republicans. Presidential candidates struggle to reconcile the views of the many conservatives with those of the broader electorate, and the shape of the contest encourages narrowcasting to the base.

Party leaders in Congress fight rear guard actions by conservative rebels. It’s hardly regular order when one senator (Ted Cruz of Texas) calls the leader of the party (Senate Majority Leader Mitch McConnell of Kentucky) a liar. Or when a House backbencher (Rep. Mark Meadows of North Carolina) files a motion, however frivolous, to oust Speaker John A. Boehner of Ohio.

Republicans point to the Democrats’ problems to play down their own. Even after a summer of successes, President Obama’s approval ratings are still below 50 percent, and many in his own party oppose his Iran nuclear agreement. Clinton’s unfavorable ratings are not as bad as Trump’s, but they are hardly reason to cheer, given her standing in the nomination contest. The Democrats’ strength in the states has been decimated over the past six years. Its presidential field of candidates is the thinnest in memory.

Yet a certain burden of proof still weighs on the Republicans. They have lost the popular vote for president in five of the past six elections. Over those six elections, they have averaged just 211 electoral votes, 59 short of the 270 needed to win. For the Democrats, the average is 327. Big industrial states that once were competitive in presidential elections — Pennsylvania, Michigan and Illinois to name three — have now voted for Democratic nominees six consecutive times.

That’s not to say the right candidate could not make some of these states competitive. Maybe former governor Jeb Bush or Sen. Marco Rubio could move Florida back to the GOP after two straight Democratic victories, but population changes are helping the Democrats. Some GOP strategists think Wisconsin Gov. Scott Walker or Ohio Gov. John Kasich might put some Midwestern states back into play. But recent Republican presidential candidates have believed they could do the same, only to come up well short.

Gallup and Pew Research have delivered doses of bad news to the Republicans this summer. Late last month, Pew reported a sharp decline in the GOP’s favorability, down to 32 percent positive from 41 percent last January. Gallup found something similar in a release last week. Earlier Gallup found that Democrats had again moved ahead of Republicans in the percentage of Americans who identify with them.

What’s behind the decline in the Republicans’ favorability ratings? The Pew study showed that there was a small decline among Democrats (from 18 percent favorable to 14 percent) and a somewhat larger drop among independents (from 37 percent to 29 percent). But the biggest falloff came among Republicans, plummeting 18 points (from 86 percent favorable to 68 percent) since January.

A year from now, it is likely Republicans will have a more positive view of their party, given the natural flow of things as a general election nears and partisan attitudes harden. At this point, however, the findings show a party with external image problems and internal differences that reflect competing hopes, aspirations and expectations by rank-and-file Republicans.

The coming week will be all about the candidates, with a forum, a debate and a conservative gathering packed into the next seven days. If you are already weary of Campaign 2016, this might be the week to go off the grid. On the other hand, why turn away at this moment, just as things could get more interesting?

The events begin Monday, when 14 candidates will attend a forum on the campus of Saint Anselm College. The event is sponsored by the New Hampshire Union Leader newspaper and local television stations from that state as well as Iowa and South Carolina. It will air nationally on C-SPAN. Only Trump and former Arkansas governor Mike Huckabee will be absent. The format calls for all 14 to be in the room and called to the stage individually to answer questions.

On Thursday, the top 10 candidates, based on the average of recent polls, will take the stage in Cleveland for the first nationally televised debate. It will be aired on Fox News. It will be one of just nine debates sanctioned by the Republican National Committee for the nominating season. The prime-time debate will be preceded by an earlier forum that day for those who did not qualify for the main event.

At the end of the week, many of the candidates will troop to Atlanta to appear before an audience of conservatives and activists at a conference hosted by the organization Red State. Their appearances will coincide with the post-debate cavalcade of spin and chest-beating about what happened in Cleveland.

Right now, it’s anybody’s guess what a majority of Republicans are looking for in a nominee. There are simply too many choices. The typical voter is far behind the media and some activists in making judgments. Polls capture name identification and the emotions of the moment, but they are hardly indicators of the future.

Trump’s blunt talk has brought him a surge of support. Others in the field still doubt he is a credible threat to win the nomination but fear his impact on the party. Bush more than others has his focus on expanding the party’s support among Hispanics and African Americans, yet he stirs few real passions within his own party’s base. Walker is the only other GOP candidate with a double-digit average in the polls. Some of the others have pockets of support but few in the field are not well known.

Four years ago, the nomination process did not serve Republicans well. Mitt Romney hurt his own cause and the rest of the field underwhelmed the electorate. In Cleveland, the candidates’ checklists will be personal: to make a good impression, avoid miscues and, no doubt, hope that Trump has a bad night. Together, they will begin to define the future shape and priorities of a party. The candidates may not be thinking much about that right now, but there will be consequences to the collective face of the GOP that they project.