(CNN) Mitt Romney is the latest Republican to go after President Donald Trump. But there's one major difference between Romney and most other Trump critics: Romney's home state.

Romney is in the perfect state , Utah, to launch his anti-Trump attacks from. He is far more likely to have the Republican base back home support him than other anti-Trump Republicans are.

Trump won just 14% of the vote in the 2016 Utah Republican caucus. It was one of only two caucuses or primaries where Trump finished lower than second, and the only one where he took less than 20% of the vote.

Trump also did worse among Utah Republicans in the general election -- winning just 64% of them -- than he did among Republicans in any other state. His poor performance was due in part to the strength of conservative Evan McMullin, who launched a third party bid to provide conservatives who didn't like Trump with an alternative.

Romney did much better in his Senate bid in Utah than Trump did in his presidential bid in the state. Even after his anti-Trump rhetoric during the 2016 campaign, Romney won 71% of the vote in a primary against Republican Mike Kennedy in 2018. That's 57 points higher than Trump did in the 2016 caucuses. (I should note Trump endorsed Romney's 2018 Senate bid.)

The general election shows the same picture of Romney outperforming Trump in Utah. Trump won only 45% of the vote in the 2016 general election. Romney won 63% of the vote in the 2018 Senate race -- 18 points higher than Trump in 2016.

Among Republican voters, an Associated Press/Fox News Voter Analysis found that Romney won 91%. (This "analysis" does not meet CNN's standards because it uses non-probability sampling .) In other words, Romney scored 27 points higher with Utah Republicans in 2018 than Trump did with them in 2016.

There is no sign that Trump has become significantly more popular in the state since his relatively poor 2016 showing. His approval rating among all voters in the state was 47% in the Associated Press/Fox News Voter Analysis. That's nearly identical to a 2017 yearlong Gallup poll , which put Trump's approval rating at 48% with Utah residents.

More to the point, Trump's approval rating among Romney's 2018 voters was only about 65%, per the Associated Press/Fox News poll. Romney's favorable rating among these voters was about 95%.

It's important to understand how different the dynamic is in Utah compared with what it is nationally for other Republicans and what it was for the Senate's last chief Trump critic, Jeff Flake in Arizona. Arizona's Republican base looks a lot more like the Republican base nationally than it does Utah's.

Trump won Arizona in the 2016 primary just like he won the nationwide primary. He also took Arizona in the general election, thanks to the support of 88% of Republicans, which is the same percentage of Republicans he won nationwide . Trump's Republican backing in Arizona and nationally was 24 points higher than it was with Utah Republicans in the 2016 general election.

This year we see the same story. Trump's approval rating was about 95% among those who voted for Arizona Republican Senate candidate Martha McSally, according to the exit polls . That's about 30 points higher than it was among those who voted for Romney in Utah, but about equal to the around 90% approval rating Trump enjoyed among those who cast ballots for congressional Republican candidates nationwide.

To put a ribbon on it, only about 30% of Romney voters said their votes for him in Utah were meant to express support for Trump in the Associated Press/Fox News Voter Analysis. In the same analysis, a majority of those voting for McSally in Arizona, as well as those voting for Republican congressional candidates nationwide, said their votes were meant to express support for Trump.

Put another way, Republicans in Arizona and nationwide were much more eager to have Republican members of Congress back Trump than Republicans in Utah were. Romney has much more room to criticize the President.