FILE - In this April 15, 2015, file photo, Republican presidential candidate Sen. Marco Rubio, R-Fla., discusses their recently released tax reform plan at the Heritage Foundation in Washington. Rubio lacks the experience to be president and Jeb Bush is a brilliant man ready for the job. So said Marco Rubio. Thing is, that was Rubio a few years ago, a man of seeming humility who joked that the only thing he deserved being president of was a condo association. He dismissed in colorful terms the idea that one term in the Senate could make a man ready for the White House. (AP Photo/Molly Riley, File) Sen. Marco Rubio (R-Fla.) at the Heritage Foundation in Washington in April. (Molly Riley/Associated Press)

If you look at early polls, fundraising, campaign staffing and media acumen, Wisconsin Gov. Scott Walker and Sen. Marco Rubio (R-Fla.) appear to be the two strongest opponents to take on Jeb Bush. What are Walker and Rubio doing right, and why have they separated themselves from the rest of the pack?

Certainly, their newness is part of their appeal. They are a generation (at least) behind Hillary Clinton and congressional leaders of both parties. They are relatively new to the national stage for many voters. They can credibly claim to be outside the permanent political class. Perhaps because Clinton is so very stale, Republicans seem to relish having young, fresh contenders. They each have a success story — Rubio’s is based on the immigrant experience, and Walker’s is rooted in a modest Midwestern upbringing. They are personally religious, but they do not come across as scolds. Neither has gotten rich off politics, and in fact, both (like a lot of Americans) carry some household debt.

Neither of these candidates relies on shopworn excuses or bogeymen. They don’t spend time railing at the mainstream media. They don’t claim that Christians are imperiled (although they defend “religious liberty”) or that our government is on the verge of a dictatorship. They don’t make absurd proposals (Abolish the IRS! Ignore the Supreme Court!), nor do they subscribe to the anti-government rhetoric we hear from some candidates.

Temperamentally, despite their youth, both project calm and eschew anger. Walker is more fiery and pugnacious, more likely to show some bravado having survived a recall and two elections. Rubio is among the most adept candidates when it comes to TV or any Q&A format; Walker now navigates through interviews on a variety of topics.

They approach government as problem solvers. They present a strain of conservatism that is principled but also pragmatic, and they do not decry compromise or bipartisanship as selling out. Rubio has a boatload of policy ideas, plus a foreign policy vision that seeks to rebuild American credibility and power. Walker has yet to zero in on national policy specifics but has begun reminding audiences of his list of state accomplishments (e.g. taming the teachers union, tax cuts, balanced budgets, pro-Second Amendment legislation). On foreign policy, he now offers clear critiques of the president’s failures and has adopted a mainstream-hawkish stance.

In short, these are young and energetic, hawkish conservatives who appeal to the base but have a temperament and record that “establishment” conservatives find reassuring. And most important, each has a message, one they can credibly deliver and which is in sync with their biography. Walker is going to fight for the middle class against government special interests; Rubio is going to promote upward mobility in a new century.

It is no accident that some in the party are already thinking the two may be on a ticket together. Like Clinton-Gore, they would reinforce a reform-oriented message and offer a generational shift from one era of leadership to another.

Neither one of them might be the nominee, to be certain. Bush remains a force to be reckoned with and will have the money and organization to undertake what looks to be more a marathon than a sprint. As between the two not-Bush contenders, it may come down to who is best able to become the complete candidate for whom voters search.

Rubio will need to put voters’ minds at ease about his executive skill and grittiness. He will need to come to terms with two significant failures in judgment — support for the shutdown and a baffling aversion to use of force against Syria to enforce the red line. (Both can be seen as efforts to get back in the graces of the right wing after immigration reform.)

Walker will need to show off domestic and foreign policy chops. He cannot build a campaign purely on anti-union fervor, both because it is not the solution to what ails the country and because it suggests another era of confrontation and division. Walker’s task may be easier (you can learn foreign policy, and he can highlight the rest of his record), but Rubio is the more skilled, natural politician.

Nevertheless, even with these shortcomings, Rubio and Walker have already distinguished themselves. It is not by accident these two candidates are doing well. And it’s not clear who has a leg up on the other, but together they would certainly provide a powerful contrast to the 67-year-old, scandal-ridden grandmother who got rich off government.