Julian Zelizer is a history and public affairs professor at Princeton University and the editor of " The Presidency of Barack Obama: A First Historical Assessment ." He's also the co-host of the "Politics & Polls" podcast. Follow him on Twitter: @julianzelizer . The opinions expressed in this commentary are his own.

(CNN) Mitt Romney had a tough day in Utah. The former Massachusetts Governor and Republican presidential nominee lost in the nominating caucuses to state representative Mike Kennedy at the Utah GOP Convention.

Not only did Romney fail to reach the 60% vote needed to secure a place on the November ballot, but Kennedy took the lead in the second round of voting with 50.88%. Romney, one of the most well-known Republicans in the country, came in second place with 49.12% of the vote. Now Romney must compete in a primary to see if he can make the final cut.

Romney is a perfect symbol of the confused state of many Republicans who do not sit squarely within President Donald Trump's political camp. For a brief spell during the 2016 campaign, Romney re-emerged on the political stage when he billed himself as the top "Never-Trumper" with a widely-publicized speech calling Trump a "fraud" and a "cheat."

Not surprisingly, when Senator Orin Hatch was debating whether to retire, Trump strongly encouraged him to run for the Senate again -- slighting Romney, who was considering a run for Hatch's seat.

And yet Romney has also tried to endear himself to Trump -- particularly when he was eager to jump into the Secretary of State sweepstakes. And recently, he has remained relatively supportive of the administration. Indeed, during his tour of Utah, he has been explaining to voters the similarities between himself and the President on many key issues, including taxation and public control of land. On immigration, Romney boasts that he is far more conservative than the President.

Romney's story is not unique, and the impact on Republican candidacies in 2018 could be a huge boon to Democrats as they seek to regain control of Congress. While his unstable governance style and embrace of radical populist ideas on issues like immigration might end up working for Trump as president, the Republican Party and its leaders could end up paying a steep price for allowing this presidency to happen and for continuing to support it.

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Like Romney, most Republicans have stood by Trump. Similar to Senators Bob Corker (R-TN) and Lindsay Graham (R-SC), Romney has offered strong words about what the President is doing wrong but then generally remained a loyal party foot soldier to the Commander in Chief. His transformation into a Trump supporter during his effort to win over the conservatives at the Utah convention was yet another indication that when push comes to shove, most in the GOP are not willing to break with the President.

In Romney's case, it wasn't enough. Many party leaders and activists still don't forgive Romney for his blistering campaign speech. Speaking to a reporter at the Utah convention, one delegate said , "If he [Romney] would have succeeded in bringing down Donald Trump, we most likely would have ended up with Hillary Clinton."

The GOP will now rise or fall as the Party of Trump. Republicans like Mitt Romney have been the strongest proof that there is no great distance between themselves and the President. While many social conservatives still like to complain about Trump's Playboy values and "mainstream Republicans" don't like his governing style, most have not taken any kind of serious steps to stop him.

Most Republicans in Congress have voted for his bills, and they have not tried to check his executive orders through legislation. House Republicans have shut down the investigations into the administration and devoted more energy to going after the investigators. Many Republicans who have been extremely critical of the president in public have later cozied up to him on the golf course.

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The midterm elections will be the first test of whether Republicans will pay a price for the Romney-like embrace of this unconventional presidency. If recent polls showing a diminished Democratic advantage turn out to be true, then Republicans will likely stand by their man for the rest of his term or two terms. The current vacillation about whether some Republicans would endorse Trump, including from Romney, is nothing more than politicians hedging their bets.

If Democrats regain control of Congress, however, that might be the only thing that actually stirs more Republicans to openly oppose this administration by joining Democrats in a bipartisan coalition to reverse his agenda and by pouring resources into members of the party seeking to challenge him in 2020.

Until then, however, most Republicans will still be part of a party, as defined by the Romney perspective, who are simply holding their noses, toeing the party line and waiting to get through the rest of the term without sticking their necks out against Trump.