Julian Zelizer is a professor of history and public affairs at Princeton University, and author, with Kevin Kruse, of the forthcoming "Fault Lines: A History of the United States Since 1974." The opinions expressed in this commentary are his own. View more opinion articles at CNN.

(CNN) Sen. Mitt Romney told the country in a Washington Post op-ed Tuesday that President Donald Trump does not have the character to be president. Careful to explain that he agrees with most of the President's tax policies, lest Republican voters think that he has veered to the left, Sen. Romney expressed worry that Trump has not lived up to the nation's ideals.

Sen. Romney's statement is not a profile in courage. Rather it is another example of the emptiness of the #nevertrump movement -- all talk and no action. Indeed, Mitt Romney essentially invented the brand. He was Jeff Flake before Flake started to complain. (This point is not lost on Trump, who tweeted Wednesday, "Here we go with Mitt Romney, but so fast! Question will be, is he a Flake?")

During the 2016 presidential campaign, Romney famously made a blistering speech about why Trump should not be president. He mocked Trump's failure as a business leader and condemned the way he conducted himself in public. Romney took center stage to warn his party against going all in for Trump, using tough words to paint the reality television star as a person who could not be trusted with the keys of power.

Then, Romney did nothing. He even dined with Trump as talk swirled that he could be the new President's secretary of state nominee. Until now, Romney has remained largely silent during most of the Trump presidency.

Other Trump GOP critics such as Flake or former Sen. Bob Corker offered endless statements about what is wrong with the President, then, like Romney, took virtually no action to demonstrate their opposition or to constrain his power. They mostly watched as the President bashed key institutions and took dangerous steps to undermine law and order. And then they both left the Senate.

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