Donald Trump finished up the primaries weeks ago, but he can’t stop running against imaginary Republican opponents.

The presumptive GOP nominee has struggled in his transition to the general election, and recent surveys show his national support dropping fast: Just over 38 percent of voters back him, according to an average of polls by Real Clear Politics, his worst showing since August 2015.

A major part of his problem appears to be Trump’s bizarre insistence on emphasizing topics that divide his own party and unite his opposition. These include his complaints about Judge Gonzalo Curiel’s “Mexican heritage,” Trump's repeated sniping at Republican politicians, his renewed call for a ban on Muslim travel and his broader response to the Orlando terror attack, among other topics.

Normally, the post-primary period is a good time for a nominee to do the reverse. A frequent tactic is to find a “wedge issue,” a position on a prominent debate that excites the candidate’s base but forces their opponent to risk upsetting different groups within their party.

As The New Republic’s Brian Beutler notes, "wedge issues" have a long and storied history. Richard Nixon, for example, famously used crime in 1968 to split black voters and blue-collar whites, two key Democratic voting blocs. George W. Bush used issues like terrorism and gay marriage in 2004 to put Democrats on the defensive with conservative swing voters. In the next election, Barack Obama used the Iraq War’s unpopularity to do the same with Republicans.

Related: Ryan Instructs Republicans to Follow Their Conscience on Trump

Rather than find a similar issue, Trump seems obsessed with topics that Democrats are perfectly comfortable to address, but that leave Republicans scrambling to avoid comment.

Why are Republicans running away? The polls tell the story.

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To start, Trump’s prolonged campaign against Judge Curiel drew a furious response from Republican leaders. An online YouGov/Economist poll asked voters two questions on the topic: whether they felt Trump’s argument that the U.S.-born Curiel was biased because he was “Mexican” was correct, and whether they felt Trump’s comments were “racist.”

The results indicate a deadly wedge issue for Republicans. The majority of total respondents, 57 percent, thought Trump's suggestion that Curiel was biased was incorrect, versus just 20 percent who felt Trump was right. But Republicans were perfectly split, with 39 percent saying Trump was incorrect and 43 percent saying that he was right. Total respondents called the comments racist by a 51-32 overall margin, but Republicans thought they were not racist by an even wider 65-22 margin.

Remember: Trump asked for this debate. It began after he devoted more than 11 minutes to attacking Curiel in a speech to supporters. But given those numbers, it’s not hard to see why Republicans including House Speaker Paul Ryan and Majority Leader Mitch McConnell were so quick to run away.

How about Trump’s reaction to Orlando? Similar problem. Trump congratulated himself on his foresight, renewed his call for a ban on Muslim travel and vaguely accused the president of a secret agenda that might prevent him from stopping terrorism.

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The intention seemed aimed to put Democrats on the defensive about their competence and willingness to protect the country. Instead, it had the opposite effect: Democrats not only denounced Trump’s comments without a second thought, but they immediately pushed Republicans do the same, many of whom sounded deeply uncomfortable discussing the subject at all.

Like the Curiel attack, polling suggests Republicans might have good reason to run from Trump’s response.

A Bloomberg poll this week found 51 percent of likely voters were bothered “a lot” and 15 percent “a little” by Trump’s call for a temporary halt to Muslim visitors in the United States. This was close to their findings on the Curiel story, which bothered 55 percent of likely votes “a lot” and 17 percent “a little.”

Bloomberg declined to release crosstabs on the poll by party, but Ann Selzer, the veteran pollster who conducted the survey, confirmed that a “solid majority” of Republicans were not bothered by the Muslim ban.

A CBS News poll taken after the Orlando attack also found 62 percent of adult respondents opposed the Muslim ban, versus 31 percent who expressed support. Just 25 percent approved of Trump overall. The numbers were better in an NBC News/SurveyMonkey poll out Thursday that found half of Americans in favor of a ban versus 46 percent opposed.

Trump’s recent spats seem unlikely to produce different results. Recently he announced he would welcome North Korean dictator Kim Jong-un to talks in America, a position Republican officials are highly unlikely to support based on their longstanding objections to talks with rogue states like Iran. Trump has also continued to attack Republican critics, including former nominee Mitt Romney and former GOP rival Jeb Bush, something that almost by definition only divides the party.

Creating divisive fights is an added problem for Trump, because one of his signature issues – immigration – is already a classic wedge between Republicans. Trump advocates rapidly deporting all 11 million estimated undocumented immigrants by force, but polls consistently show Americans favor a path to legal status by a wide margin.

Related: Obama Blasts Trump's Muslim Ban: 'Where Does This Stop?'

A Pew Survey in March found 75 percent of voters support earned legalization for immigrants, including 59 percent of Republican respondents. In exit polls of GOP races, Republicans favored deportations over earned legal status in just two out of the twenty states where the question was raised. Republican officials are divided on the topic as well, and few hardliners openly call for mass deportations, as Trump has done.

There are certainly opportunities for Trump to find topics that put Democrats on the defensive. At the top of the list are concerns about Hillary Clinton: The same Bloomberg poll that found voters upset with Trump’s positions on Curiel and Muslims also found widespread concerns about Clinton’s use of a private email server as Secretary of State, as well as her paid speeches to Wall Street banks.

Republicans would surely rally to Trump’s side if he made them a focus of his campaign, but he’s so far been unable to concentrate on his opponent for too long without slipping into one of his more divisive issues and then hunkering down once Republicans criticize him over it. At some point, Trump has to ask himself which party he’s running against.