President Trump’s advisers see Senator Bernie Sanders as their ideal Democratic opponent in November and have been doing what they can to elevate his profile and bolster his chances of winning the Iowa caucuses, according to Republicans familiar with the plans.
But their new focus on Mr. Sanders, independent of Vermont, comes at a time the president himself has been closely watching Michael R. Bloomberg, a late arrival to the Democratic primary race, unnerved by his campaign spending and his suggestion he might spend $1 billion of his own fortune on opposing Mr. Trump, even if he does not emerge as the nominee.
It has left the president and his campaign focused on two different candidates in the weeks before Democrats cast their first votes in Iowa — one, a populist running with a grass-roots movement behind him, and the other, a liberal billionaire who could refashion the general election because of his bottomless bank account.
Neither is the national front-runner, but Mr. Sanders is believed to have gained significant ground in Iowa, and both are on the minds of the president and his team.
Most of Mr. Trump’s advisers see his biggest looming threat as Vice President Joseph R. Biden Jr., who has maintained a steady level of support despite an onslaught of attacks from the president and his team. But there is often a divide between how Mr. Trump and his aides view opponents.
Over the past few weeks, aides to the president in a series of conversations have discussed how to keep the focus on Mr. Sanders, the self-described democratic socialist who favors a significant expansion of government health programs and who is currently at the top of some Iowa polls. They see attacking him as a way to excite his base and draw attention away from other Democrats.
Such efforts tend to be haphazard and revolve around Mr. Trump’s comments at rallies and on his Twitter feed, as does much of the messaging of his campaign. The president, his advisers say, has been in need of a clear target for months, and he believes he is actually hurting Mr. Sanders.
Mr. Trump’s advisers do not necessarily share that view. But they find utility in trying to elevate Mr. Sanders, and aides are discussing ways to keep attention on Mr. Sanders in the lead-up to the Iowa caucuses on Feb. 3.
“Wow! Crazy Bernie Sanders is surging in the polls, looking very good against his opponents in the Do Nothing Party,” Mr. Trump posted Sunday on Twitter, after a Des Moines Register poll showed Mr. Sanders leading in the state. “So what does this all mean? Stay tuned!”
“It means you’re going to lose,” Mr. Sanders tweeted in response.
At a rally last week in Toledo, Ohio, the president singled out Mr. Sanders for his criticism of Mr. Trump’s Jan. 3 drone strike that killed Maj. Gen. Qassim Suleimani at Baghdad International Airport.
“Bernie is going up,” Mr. Trump said. “He’s surging. Crazy Bernie is surging.”
Most of the president’s advisers see Mr. Sanders, if he were to become the nominee, as helping to solve Mr. Trump’s problem with suburban voters in states like Virginia, where the 2018 midterm elections showed that moderate and independent voters have recoiled from the president’s behavior, controversies or policy positions.
But some have concerns that Mr. Sanders might be more durable in the Rust Belt states, like Michigan and Wisconsin, with high concentrations of white working-class voters that emerged as trouble spots for the president in the 2018 elections.
The advisers say that in their voter research Mr. Sanders registers with his own supporters as authentic — the same quality that Mr. Trump’s base ascribed to the president in 2016. They view Mr. Sanders as a more difficult opponent than Senator Elizabeth Warren, Democrat of Massachusetts, but less of a challenge than Mr. Biden.
And Mr. Trump’s advisers are discussing rolling out policies to counter Mr. Sanders’s populist appeal.
In recent days, Mr. Trump’s team has been interested in focusing attention on Mr. Sanders’s comments after the strike that killed the General Suleimani, arguing that he will appear too dovish for the general electorate.
“We have no preference in potential opponents because President Trump will beat any one of them handily,” Tim Murtaugh, a Trump campaign spokesman, said in a statement. “However, over the last two weeks Bernie Sanders has proved himself to be dangerous — not as an opponent but as a potential president — by excusing and appeasing Iran’s aggression and belligerence.”
“Bernie Sanders would not protect American interests as president and his weakness is something that begs to be highlighted,” he added.
Mr. Sanders’s campaign manager, Faiz Shakir, pointed out that Mr. Trump ran as the candidate who “would stop the endless wars” and is now attacking the senator as weak. He added of Mr. Trump’s efforts to tar Mr. Sanders: “There’s no ‘there’ there.”
As for Mr. Bloomberg, the president has made clear he is aware of the money Mr. Bloomberg, a former New York mayor, is pouring into the race — especially into the attack ads hitting him in 118 media markets across the country. And this week he responded on Twitter to a TV spot focused on the top issue for Democrats in the 2018 midterms: health care.
“Mini Mike Bloomberg is spending a lot of money on False Advertising,” Mr. Trump tweeted, going on to misrepresent his role in the health care debate. “I was the person who saved Pre-Existing Conditions in your Healthcare, you have it now, while at the same time winning the fight to rid you of the expensive, unfair and very unpopular Individual Mandate.”
Bloomberg aides noted that the ads highlight a core weakness for Mr. Trump, one that he seemed cognizant of defending himself over.
“My view from watching the president’s tweets is that he is clearly seeing our ads, he’s clearly concerned about their impact,” said Howard Wolfson, a senior adviser to Mr. Bloomberg. “It’s a massive television buy that is nationwide, attacking his biggest vulnerability and contrasting his failed record on health care.”
Mr. Bloomberg spent over $100 million in 2018 through his super PAC, involving himself in two dozen races across the country, and that has made him and his team confident they have identified his weaknesses.
“We amassed an enormous amount of data about what works in terms of identifying targeting the president’s vulnerabilities,” Mr. Wolfson said.
But the Trump campaign has waved away concerns about Mr. Bloomberg’s spending, arguing that it will only encourage Republican megadonors like Sheldon G. Adelson to spend more money for Mr. Trump.
Despite Mr. Trump’s own history of upending expectations of which candidates succeed, his aides insist they do not view Mr. Bloomberg as a serious contender for his party’s nomination, and they believe that the power of his money, noting that Mr. Bloomberg’s aides would be legally prohibited from direct coordination with the Democratic nominee’s campaign, unlike the national party committees.
“Hillary Clinton said she ‘inherited nothing’ from the D.N.C., which is as broke today as it was when she lost,” said Mike Reed, a spokesman for the Republican National Committee. “Growing a $300 million data-driven field operation like we have at the R.N.C. takes years. Liberal billionaires can spend as much outside money as they want, but the eventual nominee cannot coordinate with anything they build.”
Campaign finance experts, however, said the Trump campaign and the R.N.C. are underestimating the effect of Mr. Bloomberg’s cash infusion into the race and that Mr. Trump is right to be concerned.
“If Bloomberg does this, it will be unprecedented in American history,” said Fred Wertheimer, the founder and president of Democracy 21, a nonprofit watchdog group. “They will probably have more organizers than the R.N.C. will have. They will have loads of people in the battleground states, they’ll have TV ads, they’ll have digital ads.”
“It will neutralize any financial advantages he thought he had,” Mr. Wertheimer said, referring to the president, “and if they’re not worried, they’re kidding themselves.”
Whit Ayres, a Republican pollster, agreed that Mr. Bloomberg should not be dismissed.
“By any traditional measure, it’s a pipe dream, but if we learned anything in 2016 it’s that just because something has never happened before doesn’t mean it can’t happen now,” he said. “No one has ever talked about spending remotely as much money as he’s talking about spending on this race.”