Jim Messina, campaign manager for former President Barack Obama's successful re-election campaign, predicted that Sen. Bernie Sanders, I-Vt., would be unable to counter President Trump's economic messaging and would therefore lose in a 2020 electoral matchup.

"Bernie Sanders is unlikely going to be able to stand up to the constant barrage that is Donald Trump on economic issues," Messina said during the Powerhouse Politics podcast this week.

Messina contended that swing voters were "incredibly focused on the economy" and that winners of the last five presidential elections were those candidates who were able to "win" the economic argument with swing voters.

Sanders already leads the pack of declared, Democratic candidates in polling and fundraising but his poll numbers trail former Vice President Joe Biden, whom Messina campaigned for and is expected to announce his 2020 bid on Wednesday.

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He will enter a field already filled with more progressive candidates like Sens. Kamala Harris, D-Calif, Cory Booker, D-N.J., and Elizabeth Warren, D-Mass. Sanders, a self-described socialist, appeared to highlight progressives' growing prominence in the party when he came in second to former Democratic presidential nominee Hillary Clinton in 2016.

Multiple polls have shown both Biden and Sanders receiving more support than Trump for the 2020 general election.

Messina indicated, however, that the more progressive Sanders wasn't someone who could both grab swing voters and energize the base — a winning combo that he said former Presidents Bill Clinton, Barack Obama, and Jimmy Carter were able to achieve.

"You have to excite your base and turn out people, and you have to win swing voters. And we are going to look for a nominee who can do both," Messina said. "Today, you would say in a general election context, Bernie Sanders wouldn't be that candidate."

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The former campaign manager's comments came just as Karl Rove, who served as the chief strategist behind former President George W. Bush's 2000 electoral bid, speculated that Sanders had a shot at beating Trump.

Messina said that Sanders could win the Democratic nomination and be "the Donald Trump of 2020." While both Trump and Sanders have been described as populist alternatives to establishment candidates, the two would likely have a lot to debate about on the economy.

That could be tough for Sanders considering the numerous economic milestones — record-low unemployment, strong manufacturing growth, and surprisingly high gross domestic product — that Trump took credit for in the last two years.

Trump has attributed that economic success to his massive tax reform package, which Sanders vehemently opposed. Sanders has pushed a slew of progressive policies, including single-payer health care which set him and other progressives apart from their more moderate counterparts.

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According to Messina, the upcoming Democratic primary would provide a healthy debate between those two wings within the party.

"Overall, this is being cast as a kind of insurgent versus the machine campaign — I think that's wrong. Democrats are having a very healthy and very predictable fight about the ideological center of the Democratic party," he said.

Both Sanders and Trump will likely face scrutiny over their personal finances — Trump for refusing to release his tax returns and Sanders for the amount of money revealed in his.

During a Fox News town hall last week, Sanders fended off criticism of his and his wife's income which totaled more than $1 million in 2016 and 2017. Much of their income came from the success of their bestselling book, something for which Sanders refused to apologize.