Among those pushing for a pro-Sanders offensive is the anti-tax Club for Growth. On Monday, the pro-Trump group launched a TV ad in Iowa that attacks Sanders but does so in ways that could help him with Democrats. The commercial calls Sanders “too liberal” and says that he supports “liberal health care policies” and giving “government health insurance to everyone.” The spot also compares Sanders to Democratic heroes Barack Obama and Franklin Delano Roosevelt, and says he would spend trillions to combat climate change.

The Trump reelection effort, meanwhile, has spent much of the last several weeks focusing its attacks on Sanders — a gambit that two people close to the campaign described as a deliberate effort to draw attention to the Vermont senator. The campaign has used its Twitter account as an anti-Sanders messaging machine and urged prominent surrogates to train their fire on him. Their working assumption is that the presidential attention will only boost his standing among anti-Trump Democratic voters.

Trump himself took to Fox Business last week and declared that “Bernie is surging, there’s no question about it, and Bernie seems to be the one the party wants.”

Yet some of the president’s big-money backers say they aren’t interested in bankrolling an effort aimed at propping up Sanders. They worry his potential strength in a general election is being badly underestimated, much as Democrats wrongly discounted Trump four years ago.

The biggest fear about Sanders is that he could threaten the president’s monopoly on the outsider mantle in a way other Democrats in serious contention for the nomination cannot. Others express unease about Sanders’ energized following and worry that, as an unconventional, candidate he could inject an unpredictable dynamic into the contest. They, too, see potential parallels to Trump in 2016, when he attracted a wave of new voters.

President @realDonaldTrump on Crazy Bernie Sanders surging in the polls pic.twitter.com/9uzj6Wb5DW — Team Trump (Text FIRST to 88022) (@TeamTrump) January 22, 2020

Others say Sanders has struck a nerve with his focus on kitchen table issues both parties have long overlooked. Last week, Trump favorite Tucker Carlson used his Fox News show to warn that Sanders' push to forgive student debt could win “many thousands” of past Trump voters.

“Bernie Sanders poses the greatest risk because we are still in an anti-establishment era for presidential elections,” said North Carolina Rep. Mark Meadows, who is widely regarded as a potential future Trump White House chief of staff.

Others in Trump's orbit adamantly disagree. Unlike Joe Biden, they say, Sanders would be easy to brand as outside the mainstream — even providing an opening for Trump to make up ground with suburban voters who’ve deserted him. Senior Republicans say they have conducted focus groups and found that suburbanites are turned off by the senator’s politics.

“I’m of the school that says running against Bernie would be a gift,” said former Minnesota Sen. Norm Coleman, the national chairman of the Republican Jewish Coalition, a pro-Trump group that is expected to spend heavily in support of the president.

“In the end,” Coleman added, suburbanites aren’t “going to vote for a socialist.”

The Club isn’t the first conservative group to try to prop up Sanders in a Democratic primary. Ending Spending Action Fund, a conservative group tied to Republican mega-donor Joe Ricketts, aired commercials in the final days leading up to the 2016 Iowa caucuses labeling Sanders “too liberal” and outlining his positions on issues like health care.