The Trump campaign has taken preliminary steps to ensure the president gets through a primary unscathed.

Still, an INSIDER survey conducted on SurveyMonkey Audience found that a quarter of Republicans would probably back a primary challenger, and another 18 percent would seriously consider doing so.

A majority of Republicans would probably or definitely back the president in the primary against a challenger, but a contender doesn't have to win to be a headache for the President.

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While all eyes are on the Democratic primary, the President still may face a primary of his own on the Republican side. Already former Massachusetts governor Bill Weld has announced his plans to explore a run against the President, and Maryland Gov. Larry Hogan and former Ohio Gov. John Kasich are also eyeing a lane in the primary.

The core question remains, is there a constituency in the GOP for a candidate that is not President Trump in 2020 and is that constituency large enough to legitimately threaten the president's prospects?

An insurgent run against a sitting president has little recent precedent for success, but could signal larger issues or challenges for a campaign.

Read more: No sitting president has survived a serious primary challenge in the past 50 years. Here's why Trump should be worried.

As part of our recurring poll looking at the 2020 primary, INSIDER surveyed 1,144 American adults from April 26-27, 2019 and asked about their views of the primary.

We asked any respondent who said they weren't going to participate in the Democratic primary "What best describes your view about the prospects for a Republican primary in 2020?" Based on the answers from respondents who identified as at least slightly conservative:

33% said "I fully back President Trump and would absolutely not consider voting for any Republican primary challenger."

19% said "I'd probably back President Trump, but I would listen to a qualified primary challenger."

18% said "I support the president, however I am open to other qualified Republican primary challengers."

11% said "I would probably support a qualified Republican candidate who challenged President Trump in the primary."

13% said "I would absolutely support a qualified candidate who challenged President Trump in the Republican primary."

On one hand, that poses some serious challenges for the candidacy of candidates like Bill Weld. Not only would they need to present as a qualified candidate, they're also have to contend with the reality that just over half of Republicans said they'd at least probably support the president even if they did hear him out.

READ MORE: How the INSIDER 2020 Democratic primary tracker works

On the other hand, the pains that the Trump campaign has taken to lock down preliminary support in primary and caucus states start to make a lot of sense. Nearly a quarter of right-leaners would prefer a challenger. A full 42% of the right are at least open-minded to someone challenging the sitting president for the nomination.

When one out of eight Republicans appear to remain firmly on the Never Trump train, the early groundwork laid by the President's re-election effort to make the primary landscape more favorable makes sense.

Determining the feelings of GOP-aligned adults is actually a bit trickier than polling their counterparts on the left.

There were 362 respondents who said their political beliefs were slightly, moderately, or very conservative compared to the 311 respondents who said they'd likely vote in their state's Republican primary or caucus.

Republicans are a little more difficult to poll than you might think: only a quarter of the country identifies as Republican, with people who lean left are more likely to unambiguously identify as Democrats. This isn't to say there are fewer people who lean right than left, but it does mean that loads of them identify instead as independents. As such it's worth considering not only the people who said they'd likely vote in a Republican primary, but also people who identified as slightly conservative or more.

Those who said they'd vote in the primary were more surefooted (35% backed the president totally, 20% would probably back the President, and 14% would absolutely back a challenger) but the same pattern overall held.

As a caveat, this sample size isn't ideal, and given the over 30 million votes cast in the 2016 primary we'd put the margin of error down at closer to +/- 5 percentage points than the +/- 3 in the overall set, but we'll be running this question several times over the next few months to monitor the race.

SurveyMonkey Audience polls from a national sample balanced by census data of age and gender. Respondents are incentivized to complete surveys through charitable contributions. Generally speaking, digital polling tends to skew toward people with access to the internet. SurveyMonkey Audience doesn't try to weight its sample based on race or income. Total 1,144 respondents collected April 26-27, 2019, a margin of error plus or minus 3.07 percentage points with a 95% confidence level.