(CNN) Hillary Clinton picked up another Republican endorsement on Saturday when Christine Todd Whitman, the former governor of New Jersey, endorsed the former secretary of state.

Whitman has been an outspoken critic of Trump and says in her Star-Ledger op-ed that Clinton "has many faults" but "would at least walk into the Oval Office ready to govern."

Her piece -- published Friday before Trump's campaign was imperiled by a 2005 video showing him making vulgar comments about women -- is titled "Why Clinton is the only choice for president."

"In this election, voting your conscience is not a straightforward choice, but it is critically important to vote. If sensible centrists stay home because there are no great options, we risk ceding control to the fringes of our political spectrum," Clinton said. "Please consider the long-term consequences of your choice and make that choice heard in November."

Whitman, who also served as the administrator of the Environmental Protection Agency under George W. Bush, said in March -- before Trump was the nominee -- that she would back Clinton over Trump, should he secure the nomination.

"I will probably vote for her," Whitman said. "I don't want to. I can do a write-in. But I think that's where I'd go if those are my choices."

Whitman has also compared Trump to Adolf Hitler.

"It is no longer a stretch to compare Donald Trump ... to some of the worst dictators in history," Whitman wrote in December in the wake of Trump's proposal to ban Muslims from the US. "Trump especially is employing the kind of hateful rhetoric and exploiting the insecurities of this nation, in much the same way that allowed Hitler and Mussolini to rise to power in the lead-up to World War II. The parallels are chilling."

Clinton's campaign has been courting Republican endorsements for much of 2016, looking to disqualify Trump with moderate Republicans who have been appalled by some of the nominee's more shocking comments.