Hillary Rodham Clinton and Jeb Bush laid out ambitious agendas in their announcement speeches over the past eight days. If they are as good as their word, the coming months of the presidential campaign could be remembered for something unusual: a summer of substance.

Though of different parties and different philosophies, Clinton and Bush certainly share one thing in common: They are unabashed policy wonks. At Clinton headquarters, policy meetings with the candidate are blocked out in hours, not minutes. Bush, asked the other day to explain how he would achieve one of his big goals, responded, “How much time you got?”

The two candidates obviously have specific vulnerabilities unrelated to questions about their policy agendas. For Clinton it is the questions about honesty, trustworthiness and personal accessibility. For Bush, it is the resistance to his candidacy that comes with his family name and with perceptions that his conservatism is too squishy for some in his party. But both candidates say they are determined to make their campaigns about ideas and the policies to back them up.

Their mutual interest in the details of policy comes from their long experience in the public realm. Clinton has been grappling with domestic policy problems ever since she joined the Children’s Defense Fund as a young lawyer. Bush long has been known as the more policy-oriented brother in the family business of elective politics, a reputation he earned before, during and after his time as governor of Florida.

But if the two are steeped in policy, they have left themselves sizable challenges as presidential candidates. Clinton’s is to flesh out her pledge to make income inequality — the gap between the wealthiest and the rest of society — the central issue of her candidacy. Bush’s is to demonstrate that he has something fresh to back up his goal of returning the U.S. economy to sustainable 4 percent annual growth rates.

The speech Clinton delivered at the Franklin D. Roosevelt Four Freedoms Park on New York’s Roosevelt Island on June 13 offered sweeping rhetoric about the state of an economy that she said should work for all and not just the most privileged.

In tone, it was at least mildly populist. That was evidence of her conclusion that the Democratic Party’s most important constituencies are looking for something closer to the European Social Democrat views of Sen. Bernie Sanders (I-Vt.) than the New Democrat ideas that helped elect her husband, Bill Clinton, to the presidency a quarter-century ago.

As she drilled down, however, the speech became a more familiar Clintonesque approach to domestic and economic policy: a long string of policy programs or ambitions, many of them proposed before. They represent a general continuation of the approach followed by President Obama rather than any dramatic break with mainstream, conventional orthodoxy of her party.

The list of ideas included raising the minimum wage; offering paid family leave for new parents and more flexible work schedules; giving small businesses and others tax breaks to encourage long-term investment rather than short-term profit; encouraging development of alternative energy sources and discouraging the use of fossil fuels; creating an infrastructure bank for matters including highways and broadband; providing universal preschool and more access to high-quality child care; making college more affordable; giving adults incentives for lifelong learning; offering illegal immigrants a path to citizenship.

By this reckoning, Clinton is not a believer in a big-bang approach to the problems she outlined. Instead, she favors smaller steps and an array of programs, reminiscent of the State of the Union addresses during her husband’s administration.

She said in her launch speech that growth and fairness were two goals of her economic policy, though she neither established targets for growth nor signaled the degree to which a third Clinton administration would pursue policies of redistribution.

Her speech did not broach raising taxes on the wealthiest Americans, a notable omission from a Democratic candidate trying to strike a populist tone. Clinton campaign spokesman Brian Fallon said in a message that she will deliver a fuller speech later this year calling for revising the tax code and “ensuring the wealthiest Americans pay their fair share.”

In contrast, Bush established an ambitious and difficult-to-achieve growth target in his speech. “There is not a reason in the world why we cannot grow at a rate of 4 percent a year,” he said.

Not a reason, except that no recent president has managed to hit that target other than for occasional quarters. Not Ronald Reagan during his Morning in America years. Not Bill Clinton during a time when the economy created more jobs than the 19 million that Bush said his policies would deliver. Not his father, George H.W. Bush, nor his brother George W. Bush, nor President Obama — each of whom governed during times of economic downturns.

Bush’s “how much time you got” came in response to a question about whether he has new policies to reach sustainable 4 percent growth. He cited actions, including paring away regulations that he said began building up before Obama took office, reforming a tax code that has not been reformed since 1986, pushing for more development of traditional energy resources, tackling “fiscal structural problems” and reforming immigration “to rebuild the demographic pyramid” in the country. He also mentioned education and training to produce a more skilled workforce.

That is an agenda for perhaps two terms. Bush was asked how quickly he could get all this done. “All this stuff?” he responded. “I’m thinking about how I’m going to do in the Iowa caucuses right now.”

He added: “But politics should be as much about aspirational goals and about backing it up with substance and then explaining how you have the leadership skills to make it so than just about how bad things are and how bad the other guy is. And that’s what this is.”

That leaves Bush with much left to do. He has to flesh out his aspirational goals with credible and achievable initiatives. He also needs to explain how he would square his advocacy for taking care of those most in need in the context of the Republican congressional budget blueprint of House Ways and Means Committee Chairman Paul Ryan (R-Wis.) that would squeeze domestic spending.

But Clinton’s task isn’t much easier. She must try to satisfy the progressive wing of her party that is hungering for harder-edged policies to match the rhetoric of populist anger, which if the subject of trade is any evidence, she is reluctant to do. She also must balance advocacy of an agenda that calls for considerable government activism with public skepticism about government’s ability to deliver.

Past campaigns have seen other candidates with an unabashed interest in and knowledge of public policy, but rarely have there been two so obviously steeped in the details as Bush and Clinton. That presages what could be a compelling debate, even at long distance for the time being. But only if both step up to the challenge they’ve set out for themselves.