WASHINGTON — Sen. Robert Menendez just can’t shake allegations of wrongdoing.

The New Jersey Democrat is the target of a Miami federal grand jury for allegedly helping to advance the interests of a wealthy friend and campaign donor, it was reported yesterday.

The probe focuses on his ties to Florida eye surgeon Salomon Melgen, whose business dealings have repeatedly entangled the senator, the Washington Post reported.

The feds reportedly are examining Menendez’s role in pushing a port-security contract in the Dominican Republic for a company in which Melgen is an investor.

Melgen also played a central role in recently debunked charges that Menendez frequented prostitutes in the Dominican Republic.

Menendez claims he’s the victim of a GOP smear campaign.

“As we have said all along, we welcome any review, because Sen. Menendez’s actions have always been appropriate, and we believe the facts will confirm that,” said senatorial spokeswoman Tricia Enright.

Menendez had to reimburse $58,000 to Melgen for two flights on a private jet to the Dominican Republic, which the senator previously failed to report.

He acknowledged helping Melgen in a dispute about Medicare overbilling, and he championed a natural gas bill that could have benefited Melgen’s stake in a Florida company.