WASHINGTON — In a blistering speech on the Senate floor Thursday, U.S. Sen. Robert Menendez suggested that President Donald Trump’s ongoing connections to Moscow meant he could be "an agent of the Russian government.”

Menendez, the top Democrat on the Senate Foreign Relations Committee, said the actions of Trump and his aides created never-before asked questions about a president’s reaction to America’s chief rival.

“Many of us have grappled with a very difficult question about our president,” Menendez said. "It’s a question that never before could we even imagine thinking about an American president, let alone saying it out loud on the floor of the Senate.

“I’m talking about the entirely legitimate question of whether Donald Trump could be compromised by the Russian government.”

Special counsel Robert Mueller is investigating whether there was any collusion between the Trump campaign and Russian officials in 2016, a probe the president repeatedly has derided as a “witch hunt.”

Senate Republicans have refused to protect Mueller from the possibility that Trump could fire him and confirmed as U.S. attorney general William Barr, who earlier criticized the investigation and would not promise to release the investigative report when it was completed.

Menendez, D-N.J., said that it was more urgent than ever to obtain Trump’s income tax returns, which he has refuse to release, ignoring 40 years of precedent and custom.

“Perhaps it’s because I’m from New Jersey and lived through decades of Donald Trump’s questionable business dealings, but I cannot understand why anyone would flat out reject the proposition he’s indebted to Russia,” Menendez said.

“We still don’t know who is behind the vast majority of the Trump Organization projects around the world, many of which continue to this day. We have to follow the money to get to the truth. How else will we ever know why our president is either unable or unwilling to publicly stand up to Putin?”

The White House responded with a long list of actions taken against Russia, including imposing sanctions on Russian individuals and entities, condemning Russia’s attacks against United Kingdom citizens, and approving lethal aid such as anti-tank missiles to Ukraine.

At the same, time, officials said the president wants to work with Russia when possible, which means having a cordial relationship with Putin.

Menendez raised concerns as he pushed for approval of a new bipartisan bill he introduced with U.S. Sen. Lindsey Graham, R-S.C., to tighten sanctions on Russia and prevent Trump from withdrawing from the North American Treaty Organization unless two-thirds of the Senate agreed.

His speech was a catalog of pro-Russian activities undertaken by the president, from his call as a candidate for the Kremlin to hack Hillary Clinton’s emails to his apparent repudiation of the findings of U.S. intelligence agencies that Russia intervened in the 2016 election to help elect him to his meeting behind closed doors with Russian President Vladimir Putin with no other American officials present.

Menendez said he had hoped Trump would rebuke Putin for his intervention in the 2016 election, or his continued aggression against Ukraine, or his continued occupation of Crimea, or the torture and murder of his opponents, but that never happened.

Instead, Trump congratulated Putin on his election win, said Russia was right to have invaded Afghanistan in 1979 because “terrorists were going into Russia,” and eased sanctions imposed on Russian billionaire Oleg Deripaska, who has ties to Putin.

“Time and again, our president has let us down,” Menendez said. “He’s let our country down. He’s left Americans to lay awake at night asking themselves, what does Putin have on our president? Why won’t he hold Russia accountable? Why won’t he champion the values of democracy, freedom, and human rights that transcend political party, and define our greatest ideals as a nation?"

Jonathan D. Salant may be reached at jsalant@njadvancemedia.com. Follow him on Twitter @JDSalant or on Facebook. Find NJ.com Politics on Facebook.

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