President Trump and his campaign have launched their most sustained attacks yet on Democratic presidential candidate Bernie Sanders, highlighting the Vermont senator’s rising poll numbers and sharp criticism of the White House’s handling of tensions with Iran.

In a coordinated string of press statements, Twitter posts and televised digs over the past week, Trump and his allies have trained their sights on Sanders, seeking to tarnish his foreign policy credentials and commander in chief appeal. The attacks represent a shift for Trump, who had previously devoted more of his energy to criticizing former vice president Joe Biden.

Trump’s allies say the president drives the campaign’s political strategy, acknowledging that he is an avid consumer of the public polling and the cable-TV punditry that has documented Sanders’s growing strength in the Democratic presidential primary.

Trump mentioned Sanders by name 10 times during his rally last week in Ohio — more than any other candidate. He continued the attacks on Twitter over the weekend and on Monday, singling Sanders out for more direct criticism than other Democratic contenders.

“Wow! Crazy Bernie Sanders is surging in the polls, looking very good against his opponents in the Do Nothing Party,” Trump wrote Sunday on Twitter. “So what does this all mean? Stay tuned!”

Sanders, who has pilloried Trump for authorizing the drone strike that killed Iranian Maj. Gen. Qasem Soleimani, had a curt response: “It means you’re going to lose.”

Trump’s campaign has released three statements in the last week specifically attacking Sanders on foreign policy, a significant escalation that has been mirrored by top Twitter accounts managed by campaign aides.

On Monday, the campaign accused Sanders of defending “the world’s top terrorist” and “pushing a naive, dangerous policy of appeasement toward Iran.” Other aides attacked Sanders on issues ranging from student loans to human rights.

Tim Murtaugh, a Trump campaign spokesman, said the focus on Sanders is not a sign of fear of the Vermont senator or any other candidate, arguing that “Trump would beat any of them handily.”

“Over the last year, the campaign has engaged various Democrats when the opportunities have presented themselves,” Murtaugh said. “In Sanders’s case, his surge in the polls coincided with his emergence as the chief apologist for the Iranian regime. We needed to point out that he would be dangerous as president since he made clear he would appease terrorists and terror-sponsoring nations.”

Sanders, who has been staunchly opposed to America’s entanglements in the Middle East, has used the conflict with Iran to draw a contrast both with Trump and with his Democratic rivals. He has accused Trump of abandoning his 2016 pledge to extract the U.S. from costly wars and has made a direct appeal to Trump voters who are disillusioned by the president’s performance in office.

“Bernie, who has spent his entire life standing with the working class, is going to spend every moment of the general election reminding working Americans that Trump was lying when he said he would stand with them and that he would end the endless wars,” said Mike Casca, the Sanders campaign communications director. “He’s the most corrupt president in American history, and Bernie Sanders is going to sweep him out of the White House.”

Earlier this month, Sanders introduced legislation to block funding for military conflict with Iran, something he said would be “disastrous.”

“At a time when we face the urgent need to rebuild our crumbling infrastructure, to build the housing we desperately need, and to address the existential crisis of climate change, we as a nation, must get our priorities right,” he said in a joint statement with Rep. Ro Khanna (D-Calif.).

Sanders has seen his poll numbers rise and his fundraising improve as he has campaigned on bringing about a “revolution” capable of ousting Trump from office. A poll released Friday by the Des Moines Register and CNN showed Sanders narrowly leading a close race in Iowa just three weeks before the Feb. 3 caucuses there. The survey is the first to have Sanders leading in the state, and it showed that he enjoys support from 20 percent of likely voters.

Sanders raised $34.5 million in the fourth quarter of 2019, a massive sum fueled by his online fundraising machine that bested all Democratic contenders.

Some Trump allies have described Sanders’s fundraising as an impressive sign of his potential staying power in the Democratic primary.

And while most of the Trump campaign’s recent attacks on Sanders have focused on foreign policy, the president’s surrogates have ramped up their critiques of his domestic agenda as well. Aides said they expect the onslaught against Sanders to continue and intensify, as Trump uses the liberal senator as a stand-in for the entire field of Democrats.

Trump is scheduled to hold a rally today in Wisconsin, a state where Sanders has said his appeal to working-class voters could put him in a strong position to defeat Trump. Last year, Sanders embarked on a “Bernie Beats Trump” tour to highlight his strength against the president in key states.

“FACT: Bernie Sanders Is A Wealthy, Fossil Fuel-Guzzling Millionaire,” read one statement from the Trump campaign on Thursday, a day after the campaign released a statement saying he “Can’t Be Trusted To Defend American Lives.”

Sanders has cast doubt on the Trump administration’s shifting explanations for the strike that killed Soleimani, accusing the president of concocting a reason to conduct an “assassination” of a foreign official.

“The difficulty that we have, and I don’t mean to be rude here, is we have a president that’s a pathological liar,” he said Friday on NBC’s TODAY show.

Trump’s campaign has responded by trying to brand the senator as soft on terrorism, a scorched-earth tactic that has come to define the strategy of the president’s reelection bid.

“How many American children have to be left fatherless before Bernie Sanders will defend American lives?” Trump’s campaign manager Brad Parscale tweeted Sunday.

Some of Trump’s advisers say they are spoiling for a general election fight with Sanders, describing him as a “socialist” who turns off moderate voters.

“I’d rather face Bernie versus Biden,” said Bryan Lanza, who advised Trump’s 2016 campaign and transition. “Let’s have the real contrast of who these parties are. Let’s have the real debate.”

Trump appeared to egg on a battle between Sanders and Sen. Elizabeth Warren (D-Mass.) on Monday, tweeting that the two liberals are fighting over voters. He also turned his fire on former New York Mayor Mike Bloomberg, who has been running ads targeting Trump on health care and other issues.

“Bernie Sander’s volunteers are trashing Elizabeth ‘Pocahontus’ Warren. Everybody knows her campaign is dead and want her potential voters,” he wrote, misspelling the slur he regularly uses against Warren. “Mini Mike B is also trying, but getting tiny crowds which are all leaving fast. Elizabeth is very angry at Bernie. Do I see a feud brewing?”