Democratic presidential hopefuls Vermont Senator Bernie Sanders (L) and Former Vice President Joe Biden (R) participate in the tenth Democratic primary debate of the 2020 presidential campaign season co-hosted by CBS News and the Congressional Black Caucus Institute at the Gaillard Center in Charleston, South Carolina, on February 25, 2020.

Tuesday, billionaire Michael Bloomberg is on 2020 Democratic primary ballots for the first time, running against, among others, a self-described Democratic Socialist in Bernie Sanders. And eventually, one candidate will face off against America's first billionaire president, Donald Trump. Of late, the Democratic candidates have spent the campaign season boasting of any humble beginnings and defending any wealth: Biden noted the first time he ever made any real money was in 2017 during the South Carolina debate. And Bloomberg said he's giving away his own money, while accusing Sanders of having three homes while in Las Vegas. It all puts a fine point on how wealth inequality has become a rallying cry for the Democratic presidential candidates, and how it could further define the election for the Democratic nominee after that. As a catalyst in the 2020 election, the rhetoric is "more acute" than it has been in decades, Democratic strategist, speech-writer and political commentator Hamza Khan tells CNBC Make It. "I do not think it has been this severe at least since the time of Teddy Roosevelt in the last century," says Khan. (President from 1901 to 1909, Roosevelt entered office during the "Gilded Age," another era in American history defined in part by extreme wealth inequality between industrial workers and "robber barons" like John D. Rockefeller and J.P. Morgan.) According to a January Pew Research Center survey, 78% of those who identify as Democrats or lean Democratic say there's too much economic inequality in the country. (Only about 41% of Republicans or those who lean Republican agree.) So for the Democrats, the conversation around wealth inequality "will only continue to increase" and move to the "forefront," Democratic political consultant Andrew Feldman tells CNBC Make It. But how did economic inequality become a tent pole for the Democratic party's agenda in 2020? According to the experts, these are some of the specific political conditions making wealth inequality a force on the Democratic campaign trail and for the election.

The wealth gap has become a chasm

"Inequality is rising as a political issue because it keeps getting greater," Paul Begala, a Democratic strategist and former adviser to President Bill Clinton, tells CNBC Make It. In 2018, the top 10% of U.S. households controlled 70% of total household wealth, according to a white paper from Federal Reserve economists. (Up from 60% in 1989, the increase came at the expense of some of those with less wealth.) The top 1% controlled nearly 32% of household wealth in 2018. The difference between average Americans and the rich (some of whom are running for president), is stark. "If you make median income ($50,000/year), and you work hard and save 100% of your money, you'll have as much money as Mike Bloomberg...in 1.2 million years," Begala says. (Bloomberg is worth $60 billion, according to Forbes.) "If you're really well off and make $1 million a year, you will catch Bloomberg in a mere 60,000 years." (With median income would take 62,000 years to catch Trump, who is worth $3.1 billion, according to Forbes.)

It's a way to counter Trump campaigning on the economy

According to Feldman, a focus on wealth inequality will be a key way to counter the likely main point of Trump's re-election campaign: a strong economy. Though fears of an economic slowdown resulting from the coronavirus outbreak have kept stocks volatile in recent days, the Dow Jones Industrial Average is still higher than when Trump took office. And the unemployment rate has been trending lower during the Trump years as well. Feldman believes Trump is not likely to change his campaign strategy, however. "The more visible signs of a weakening economy, it hurts his argument, but I don't think he is going to stop using it." Coronavirus consequences aside, highlighting wealth inequality has been the Democratic candidates' best counter punch. During the Democratic debate in South Carolina, for example, the first question, posed to Sanders, was, "How will you convince voters that a Democratic socialist can do better than President Trump with the economy?" He responded by highlighting the wealth gap. "You're right. The economy is doing really great for people like Mr. Bloomberg and other billionaires," Sanders said. "For the ordinary American, things are not so good." A focus on wealth inequality highlights that, "even when the macroeconomic numbers seem good, there is a lot of pain underneath," according to Begala. "You have to talk about the wealth inequality gap when you talk about the challenges with our economy" otherwise Trump could "sweep [the Democrats] under the rug," Feldman says.

The wealth gap is important to Gen Z

"The fact is that the electorate has evolved since 2016," Khan tells CNBC Make It. The share of the U.S. electorate who are Gen Z voters (those born after 1996) will increase from 4% in the 2016 election to an expected 10% in 2020, according to a Pew Research Center analysis. Taken together, the voting cohort of Gen Z voters and millennials (born between 1981 and 1996) form the largest voting block, Khan points out — a projected 37% of voters. Boomers (those born between 1946 and 1964) will be 28% of the voting cohort, according to Pew. These younger voters are more diverse and have different priorities than their older voting compatriots. "The difference is what this electorate is willing to tolerate versus what elder generations have grown accustomed to," he tells CNBC Make It. So while wealth inequality "was clearly bad several years ago as well," this year's voters have different expectations, Khan says. The Great Recession, which lasted from December 2007 to June 2009 according to the Federal Reserve, is seared into the formative memories of younger voters. Younger voters haven't known boomer-generation stability, he says. "Neither generation has seen the economic stability their parents or grandparents saw, and both are highly engaged civically and motivated to organize in order to see change," Khan said.

The wealth gap is important to rural voters