Tuesday night's primary loss for House Majority Leader Eric Cantor came as a shock to some. Here are five other instances when the democratic process took the country by surprise. (Sarah Parnass/The Washington Post)

One way to read the stunning primary defeat of House Majority Leader Eric Cantor (R-Va.) is that the only way to define Republicanism these days is by what it’s against.

And that’s what worries many Republicans.

An argument is boiling within the party over whether it should offer voters an agenda that shows what Republicans would accomplish if they are returned to power or whether it should simply ride an anti-Democratic tide into the November election.

Some, including Senate Minority Leader Mitch McConnell (R-Ky.), worry that proposing a set of detailed policy alternatives is taking an unnecessary risk when so much else is going the right way for Republicans. Putting forward an agenda can inflame differences within the party and give opponents targets to shoot.

That in part was what sank Cantor, who was faulted by the tea party as too accommodating.

Cantor drew intense fire for advocating a GOP version of the Dream Act, which would enable some illegal immigrants who entered the country as children to qualify for in-state college tuition rates.

Standing in opposition may be a good electoral strategy at a moment when the president and his party are politically weak, and when most of the key battles on the political map are being fought in conservative territory.

There also is the reality that President Obama will remain in the White House for the next two years, using his veto power to make sure that Republicans cannot keep whatever promises they make.

But a no-on-everything stance provides little to begin laying a premise for the presidential election of 2016.

“There is a real problem there in terms of the Republicans being a governing party,” said former GOP congressman Vin Weber, a voice of the establishment.

That is why some are arguing that their party should put forward something that resembles the House Republican policy agendas of 1994 and 2010 — both years in which they won control of the chamber.

“The Republican leadership in both the House and Senate has to take a more proactive role in deciding what we can do, not just what we can’t do,” said former House speaker Newt Gingrich, whose 1994 Contract with America is the model that some Republicans are advocating this year. “If the election has no meaning, other than the Democrats lost, what are you going to do in January?”

As it stands, Gingrich said, his party lurches between two strategies: “Either we suicidally charge into Barack Obama and shut down the government and get beaten, or we basically do nothing and hope someday we elect a Republican president.”

Among those who would like to see their party get more specific about what it would do — and not just what it is against — is Sen. Lindsey O. Graham (R-S.C.). Once considered in danger of losing to a primary challenger, Graham beat six tea party candidates on Tuesday, easily clearing the 50 percent threshold necessary to avoid a runoff.

“Conservatism to me is not about who I hate, but about what I love,” Graham said in his emotional victory speech. “The Republican Party is doing well because the Democratic Party really screwed up. I want an alternative to the Democratic Party. I want a positive agenda laid out by the Republican Party for the American people. I want some form of the Contract with America.”

“I’m tired of complaining about Democrats all the time,” Graham added. “I want to say something positive about us.”

Graham’s win, some Republicans argue, should stand as a counterpoint to Cantor’s defeat. He ran, for instance, as a staunch supporter of giving illegal immigrants a pathway to citizenship.

Democrats “try to push a narrative that Republicans are against everything. That’s not true. Republicans are for a lot of things, like more jobs,” said Stuart Stevens, a Republican consultant who is advising embattled Sen. Thad Cochran (R-Miss.), who is fighting for reelection in a runoff against tea party challenger Chris McDaniel.

Those who would like to see that party unite behind at least a handful of agenda items say those could include, at a minimum, support for the Keystone XL pipeline and more tax breaks for small businesses.

But they acknowledge that coalescing around other issues may be impossible. For instance, it is an article of faith among tea party members that the Affordable Care Act should be repealed, but that is likely impossible to achieve while Obama remains in the White House.

And any Republican who puts forward an alternative to replace the law risks being branded as yielding to Democrats.

To the most ardent conservatives, Weber said, “anything other than total repeal is a sellout.”