In a New York Times op-ed article on Wednesday, Democratic Sen. Sherrod Brown criticized the Republican senators who acquitted Trump in his impeachment trial.

According to Brown, Republicans fear that if they speak out against Trump, the president will campaign against them and his allies with vilify them on social media and powerful platforms like Fox News.

"In private, many of my colleagues agree that the president is reckless and unfit," he wrote. "They admit his lies. And they acknowledge what he did was wrong."

Visit Business Insider's homepage for more stories.

Top Republican lawmakers have hailed President Donald Trump's acquittal in his impeachment trial as a victory for the American people and praised his policies and achievements.

But in private it's a different story, according to a scathing New York Times op-ed article by Sen. Sherrod Brown, a Democrat from Ohio, published Wednesday night.

Along with the rest of his Democratic colleagues in the Senate, Brown on Wednesday voted to convict Trump on charges of abuse of power and obstruction of Congress. All but one of his Republican colleagues — Sen. Mitt Romney — acquitted the president of both charges.

Sen. Sherrod Brown of Ohio at the NAN Conference in New York City in April. Hollis Johnson/Business Insider

In the article, Brown said his Republican senators privately believed Trump was unfit for office but were too scared to act.

"In private, many of my colleagues agree that the president is reckless and unfit," he said. "They admit his lies. And they acknowledge what he did was wrong.

"They know this president has done things Richard Nixon never did. And they know that more damning evidence is likely to come out."

Congress investigated President Richard Nixon's role in covering up a 1972 break-in at the Democratic National Committee's headquarters at the Watergate complex, but Nixon resigned before he could be impeached.

A composite image of Trump and former President Richard Nixon. Justin Sullivan/Getty Images, Charles Tasnadi, File/AP

In his Wednesday op-ed article, Brown accused the Republicans of being motivated not so much by principle and an impartial assessment of evidence as by fear.

"For the stay-in-office-at-all-cost representatives and senators, fear is the motivator," Brown said. "They are afraid that Mr. Trump might give them a nickname like 'Low Energy Jeb' and 'Lyin' Ted,' or that he might tweet about their disloyalty," referring to nicknames Trump gave his Republican presidential rivals Jeb Bush and Ted Cruz during his 2016 campaign.

"Or — worst of all — that he might come to their state to campaign against them in the Republican primary."

He also suggested they feared being subjected to a relentless onslaught of attacks by Trump's allies on social media and on Fox News, the network widely popular and powerful among Trump supporters.

Sen. Mitt Romney spoke on the Senate floor about Trump's impeachment trial on Wednesday. Associated Press

Trump is widely understood to demand total loyalty from Republican lawmakers, and he routinely humiliates and vilifies critics from the party on Twitter.

He enjoys near-unanimous support from grassroots Republicans, which he has cultivated at raucous campaign rallies from when he was running for president as well as during his three years in office.

On Wednesday he attacked Romney, the lone Republican senator who voted to convict him, and accused him of being a "Democrat secret asset."