Donald Trump’s endorsement of Mitt Romney is a very mixed blessing for the candidate.

The two men heaped praised on one another at a short press conference in Las Vegas, two days before the Nevada caucuses, of which Romney is a heavy favorite to win.

“There are some things you just can’t imagine happening in your life. This is one of them,” Romney said, staying beside Trump at Trump’s hotel in Las Vegas.

Romney showed up with Trump because the real estate mogul, who flirted with his own presidential run last year, does have popularity with the anti-establishment, Tea Party wing of the Republican Party that has been slow to warm to Romney. Trump briefly lead in polls of the GOP field last year, when he was in the midst of constantly bashing President Obama.

And Trump’s endorsement is the latest sign Republicans are beginning to accept the former Massachusetts governor as the party’s candidate and suggests Newt Gingrich is not cornering the anti-Romney vote as he expected to.

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At the same time, appearing with Trump could hurt Romney in the general election. Now, the candidate has to answer why he would appear with a man who spent much of last year hyping conservative falsehoods about where Obama was born and then started calling for the release of Obama’s college grades in what appeared to be an attempt to suggest the president isn’t smart.

Romney has generally avoided these kinds of personal attacks on Obama, but appearing with Trump could inspire the media to ask him about these issues again. And the GOP candidates, aware that some of the lies about President Obama are widely accepted in the party’s base, are wary of directly saying that Obama was born in the United States and is not a Muslim, two of the common falsehoods circulated about the president.

And Trump, outside of the GOP base, is not just very popular. As Slate’s David Weigel notes, a September poll by Fox News found 6 percent of Americans would be more likely to support a candidate endorsed by Trump, 31 percent less likely.

Endorsements rarely matter in politics anyway, as voters largely judge candidates on their own merits. But now Romney will be much closer linked to a controversial figure who likes to say outlandish things to get attention.

And a day after saying very poor people are “not my focus,” Romney is appearing with a man known for firing people on a television show.

Follow Perry Bacon Jr. on Twitter at @perrybaconjr