It’s only natural that a who’s-up-and-who’s-down leadership struggle would consume House Republicans after the stunning primary defeat of Majority Leader Eric Cantor. There’s a big hole in the party’s top echelon, and it’s got to be filled.

But after a new majority leader is selected, and the leadership slate finished, GOP lawmakers will have to figure out what Cantor’s loss means for the Republican agenda. Right now, they have no idea.

That’s because they don’t know why Cantor lost. Sure, there have been dozens of stories purporting to explain the vote, but for the moment, it’s all just guesswork.

The fact that Cantor lost by 11 points in a race in which his campaign pollster projected a 34-point lead is pretty clear evidence Cantor did not know what was going on in his district. He didn’t know how many people would go to the polls ”“ turnout was far higher than in Cantor’s primary in 2012 ”“ and he didn’t know what motivated them.

Explanations for the loss focus on a mix of policy and politics.

“We have some theories, but we have no clear proof of which one of those theories is correct,” says a well-connected Republican strategist. The operative then went down four of the most popular:

1. Cantor was on the wrong side of voter sentiment on immigration.

2. Cantor paid too much attention to Washington insiderdom and not enough to voters in his district.

3. Cantor’s ads attacking opponent Dave Brat backfired, raising Brat’s name recognition and hurting Cantor.

4. Cantor did not know how to campaign effectively because he misunderstood the electorate.

There’s no reason all of those couldn’t have played a part. But until Republicans do some research, until they talk to voters in Cantor’s district, they won’t know.

One bit of fallout from Cantor’s loss could be a setback in the effort to develop a new Republican middle-class agenda. Cantor listened closely to a group of think-tankers who are becoming known as “reform conservatives.” Less than a month ago, Cantor appeared with them at the American Enterprise Institute to roll out a new set of policy ideas ”“ on taxes, education, health care, jobs, energy, regulation ”“ designed to help Republicans appeal to voters stuck in what Cantor often called the “middle-class squeeze.” Now, the reform movement won’t by any means disappear, but it has lost one of its most powerful advocates.

That could have a practical effect in the House. Rather than an attempt to construct a far-reaching agenda, the majority leader who takes Cantor’s place might adopt a more tightly focused approach.

“I think you’ll see that, rather than a huge, broad-based 57-point agenda, it’s going to be, here are the two or three critical things that Republicans need to focus on to move forward, with a focus on economic growth,” says the GOP strategist.

Cantor’s absence could also have more subtle effects on the House Republican agenda. Much of the party’s legislative priority-setting is done in regular gatherings called ELC meetings. (It stands for Elected Leadership Committee and is pronounced “elk.”) Take Cantor’s voice away and add a new one ”“ be it Reps. Peter Roskam, Steve Scalise, Marlin Stutzman, or others ”“ and the mix will change.

Then there is immigration. Both opponents and supporters of Gang of Eight-style immigration reform have been yelling at each other in the wake of Cantor’s defeat, saying it did or did not play a decisive role in the outcome. It seems hard to deny that immigration played some role, but how much is just not clear. Again, some actual research is needed.

Whatever the answer, the fact is that immigration reform was dead in the House before Cantor lost. A solid majority of House Republicans oppose it ”“ either in comprehensive form or piece-by-piece form. A GOP leadership attempt to find consensus on a reform agenda, begun at the party’s retreat last January, has gone nowhere.

Now, time is running out. It is already June of an election year. And a Republican conference already distracted by midterms has to deal with an unexpected leadership fight. So the bottom line on immigration reform in 2014 is: ain’t gonna happen.

Cantor’s departure from the House leadership won’t upend the Republican Party’s agenda. Voters are still overwhelmingly concerned about jobs and the economy, and smart candidates will work hard to address those concerns.

But Cantor’s absence could have a noticeable long-term effect on the course of the House majority. The only problem is, like the cause of what happened on election day, we don’t know what it is.

— Byron York is chief political correspondent for The Washington Examiner.