After President Donald Trump’s reelection campaign used its massive email list to go after potential 2020 rival Sen. Bernie Sanders on two consecutive days this week, team Sanders welcomed the president’s attacks as a sign that he views the Vermont senator as a serious threat to his hopes for a second term.

“The Trump campaign knows that Bernie is their biggest threat.”
—Bill Neidhardt, Sanders’ Iowa deputy state director.

In an email Wednesday attacking Sanders for condemning the likely illegal U.S. assassination of Iranian commander Qasem Soleimani, Trump described the senator as “Democrats’ 2020 front-runner” and accused him of repeating “talking points straight from Iran’ Ayatollahs.”

“Bring it,” Sanders foreign policy adviser Matt Duss tweeted in response to the email blast, which appeared to mark the first time of the 2020 cycle that Trump’s campaign has used its list to hit the Vermont senator.

Following the Trump campaign’s second email of the week—headlined, “FACT: Bernie Sanders Is A Wealthy, Fossil Fuel-Guzzling Millionaire”—Sanders said “Donald Trump is attacking us because he knows we will beat him in the general election.”