She has been called inevitable. The can’t-be-stopped candidate. Hillary Rodham Clinton is such an overwhelming favorite in presidential primary polls that most prominent Democrats are taking a pass on challenging her.

But politics can be an unpredictable business, and those of us covering the campaign have been wondering: Is there any way a Democratic challenger could beat Clinton?

We asked three of the smartest Democratic strategists we know to imagine this situation: You are running the campaign of a liberal Democrat against Clinton. You have $50 million to spend. What is your message? How do you run against her?

The strategists agreed to sketch out a blueprint anonymously, so as not to anger Clinton. Some common themes immediately emerged.

Populism

Any Democrat who takes on Clinton should be a truth-telling populist, challenging the party from within and tapping into the energy and aspirations of the Democratic base.

This is especially crucial given Clinton’s popularity with African-Americans, a significant voting bloc in Democratic primaries. One suggestion for reaching those voters? Focus on improving policing, after a national debate and protests set off by the deaths of unarmed black men in Missouri and New York City.

Another area that the right candidate could seize upon: immigration. Pound away at Democratic leaders for not passing a comprehensive overhaul when there was a chance to do so in 2014.

Another strategist said the challenger should focus on a few big-ticket ideas, like a transaction tax on Wall Street that would finance renewable energy, and hammer the utilities for harming energy independence.

"I wouldn’t give Hillary hell. I’d tell the truth and make her think it’s hell," the strategist said, echoing former President Harry S. Truman. "I’d try to build my own momentum, not blunt hers."

Foreign policy

Given her hawkish reputation, Clinton and her top advisers have been especially alert to any signs that a left-of-center Democrat would emerge to challenge her on foreign policy.

For all the concerns about Sen. Elizabeth Warren of Massachusetts and her economic populism, the person some of Clinton’s allies kept their closest eye on regarding foreign policy last year was Sen. Christopher S. Murphy of Connecticut, a Democrat who has been critical of interventionist policy in the Middle East.

Murphy is not running for president. But there is clearly an opening to run to Clinton’s left on foreign policy.

"She’s to the right of where the party is on a lot of these issues," one of the strategists said. Clinton has traditionally favored a more muscular response in places like Syria, the source of one of her biggest policy disagreements with President Barack Obama while she was secretary of state.

That means there is space for someone to pursue what Murphy described in a February op-ed article as a "progressive foreign policy," similar to what Howard Dean did in 2003. (Dean, it is worth noting, is supporting Clinton this election cycle.)

Authenticity

For more than a decade, Clinton has tried to swat away a persistent concern about her ability to connect with voters. "Saturday Night Live" recently captured that problem in a sketch featuring an actress playing Clinton, who said of herself at one point, "What a relatable laugh!"

Years of security-infused Bubble Wrap around her travels and a wealthy lifestyle have done little to pull Clinton closer to voters.

The best hope for someone running against her, all three strategists said, was to be real. And the best environment to showcase that genuineness may be Iowa. A challenger could camp out there, have a lot of up-close voter interactions, build a relationship with activists in the state and hope to catch fire.

Clinton has always had trouble in Iowa, and she never totally connected with voters there. One of the strategists advocated saving as much money as possible to spend in Iowa for a late media push.

Any primary challenge to Clinton, of course, is a long shot. But there is a hunger among the media, if not yet the Democratic electorate, for a competitor to emerge. Former Gov. Martin O’Malley of Maryland showed how easy it was to make headlines against her when he suggested in an interview on the ABC News program "This Week" on Sunday that Americans are uncomfortable with dynastic control of the White House.

Of course, much of the advice offered by the strategists comes before Clinton has started her own campaign and has begun to articulate her vision. Often a cautious campaigner, she could surprise her detractors and be bold. She could also try to seize the populist momentum herself, complicating any challenger’s plans.

Still, even as they engaged in this exercise, these strategists repeatedly emphasized the difficulty of outrunning Clinton in the Democratic primary. Elections can appear unpredictable and ever-shifting, but they are driven by fundamentals that are not easily upended. And this time, the fundamentals in the primary — from money to organization to base of support — strongly favor Clinton.