In retrospect, it is easy to see that Eric Cantor and his aides saw more trouble brewing in his primary race than anyone was willing to admit in public.

A telltale sign was the majority leader of the U.S. House of Representatives spending millions in the primary election against a little-known college professor. Cantor had probably not spent that amount in all the party primaries combined since his election, and his district based on the Richmond suburbs is a safe GOP seat.

But the perfect storm happened: An articulate professor of extreme conservative views ran and won in a primary where only 12 percent of voters turned out.

According to Roll Call, the Capitol Hill newspaper, no majority leader has ever been ousted in a primary.

First, the winners: not only Dave Brat, the professor who crusaded against government debt and immigration “amnesty” for “illegals,” the cost of welfare, the Wall Street bailout.

There is a huge populist element to his appeal: “Big business wants immigration reform. … It’s a great deal for big business but a raw deal for the people.”

Talk-show host Laura Ingraham boosted Brat, as did some of the conservative pressure groups that have bitterly feuded with the House leadership.

Cantor is at least as articulate as Brat but part of the party leadership. Cantor’s voting record is extremely conservative by any measure, but the insurgents in the party demand perfection, and a member of the leadership, from time to time, will have to cast votes that are good for the party as a whole.

Brat criticized Cantor for voting for a farm bill, even though for Republicans to keep their House majority, they have to support the interests of the many of their members in rural districts around the country.

The irony is that Cantor today remains the most popular Republican in his district. He would thumpingly defeat Brat and a Democratic in a general election. He won’t have the chance.

Of interest to Louisiana: The departure of Cantor might open a spot in the leadership for U.S. Rep. Steve Scalise, R-Metairie, who will bid for majority whip, the No. 3 position in the House Republican leadership.

Yet, even as Washington moves on before Cantor’s political body is cold, the larger lesson for the GOP is ominous.

The perfect storm for Cantor also was about a grass-roots insurgency that demands more ideological purity than government allows.

Cantor himself was long viewed as the “tea party” spokesman within the House leadership. Yet, that status could not be maintained while making the compromises — modest though they might have been — that lead to legislation.

One can ride the tiger of anti-government rhetoric, but if one dismounts to deal with the practical problems of government, the tiger sees his next meal in the compromiser, not the Democrats across the aisle.