In a CNN interview on Monday, U.S. Senator Bob Menendez (D-NJ) sounded a note of genuine worry regarding the impact down ballot of the presidential candidacy of Democratic socialist Bernie Sanders in the event Sanders wins the Democratic nomination.

Menendez said “there’s no question” Sanders will “create a real challenge for down ballot candidates” if he’s the Democratic nominee.

“I’m thinking of my home state in New Jersey, we got three new House members. They run in districts that were held by Republicans,” Menendez told CNN. “How do they triangulate? How do they if someone like Senator Sanders is at the top of the ticket?”

The state’s senator was referring specifically to U.S. Rep. Mikie Sherrill (D-11), U.S. Rep. Tom Malinowski (D-7), and U.S. Rep. Andy Kim (D-3). A fourth Democratic Party pick up in the House in 2018, U.S. Rep. Jeff Van Drew (R-2), dealt with party volatility – and particularly his party’s rejection of him when he opposed presidential impeachment – by switching his party affiliation to the GOP.

For his part, Menendez has already called for an open presidential primary. “It is more important than ever that we take steps to insulate the presidential race from any undue influence on New Jersey’s other elections,” he said last week. “In the upcoming June Democratic primary, I would implore the county chairs to have a separate column for an open presidential primary, while allowing usual ballot bracketing for down ballot races from U.S. Senate and House races down to county and municipal government.”