An internal poll released late Sunday by one of the Democrats hoping to face Republican U.S. Rep. Lauren Boebert in Colorado’s 4th Congressional District shows Democrat Ike McCorkle leading the two-term Republican by 7 percentage points with a large number of undecided votes in the state’s most reliably Republican district.

Boebert is one of nine Republicans running for the Eastern Colorado seat formerly held by Republican Ken Buck, who resigned from Congress late last month. Voters will pick a replacement to serve the remainder of Buck’s term in a special election on June 25, on the same ballot as the state-level primary. Boebert is not running in the special election but has qualified for the Republican primary.

The survey of likely general election voters, conducted by nonpartisan firm Gravis Marketing, found McCorkle – a Marine veteran who lost to Buck by double-digit margins in the last two elections – leading Boebert 38% to 31%, with 30% of likely voters saying they were undecided.

The polling suggests that Boebert, the state’s highest-profile Republican, could be more vulnerable than other potential GOP nominees in her newly adopted district.

Another Republican seeking the nomination, Logan County Commissioner Jerry Sonnenberg, a former state lawmaker from Sterling, leads McCorkle by 6 percentage points, the poll found. That’s with nearly twice as many voters saying they’re undecided as in a Boebert-McCorkle contest.

According to the poll, Sonnenberg led McCorkle 24% to 18%. Another 57% of voters were undecided.

In January, Boebert moved into the 4th CD from the Western Slope-based 3rd Congressional District she’s represented since 2021, citing a well-funded challenge from the Democrat who came within fewer than 600 votes of unseating her in 2020.

The same Gravis poll showed Donald Trump leading Joe Biden by 13 percentage points among the district’s electorate, 44% to 29%. Third-party candidate Robert F. Kennedy Jr. polled 11%, and 16% were undecided. Trump carried the 4th CD’s electorate by 18.5 percentage points in 2020.

The difference between McCorkle and Boebert is outside the poll’s 4.3 percentage point margin of error. The survey of 529 likely voters was conducted March 27-29 using text, web-based inquires and automated, interactive calls, the pollster said in a an executive summary obtained by Colorado Politics. According to the pollster, the survey’s sample consisted of 45% unaffiliated voters, 36% Republicans and 19% Democrats. Hispanic voters accounted for 9% of respondents.

A Republican convention nominated former Parker Mayor Greg Lopez, a two-time gubernatorial candidate, to run in the special election. Democrats are scheduled to pick the party’s nominee for that election Monday night in an online convention.

McCorkle is one of four Democrats seeking his party’s nomination for both elections. In a statement to Colorado Politics, he said the poll verifies the argument he’s been making that he’s best qualified to take on Boebert – the frontrunner for the GOP nomination for the November election.

“We see in these numbers what our campaign has known for months. Among the Democratic candidates, our campaign is the only choice to beat Greg Lopez in the special election and Lauren Boebert in November,” McCorkle said in an email.

“The decision made at the convention today will impact the nation, not only the citizens of CD-4. It will determine who will fight the same MAGA agenda that sought to overthrow our government on Jan. 6. The democracy I fought so hard to defend in combat is at risk, and I hope the members of the special convention will choose me and my team to defend it.”

The other Democrats running in the district are former U.S. Senate candidate Karen Breslin and first-time candidates John Padora and Trisha Calvarese.

A Padora campaign spokesman told Colorado Politics that it would be a mistake to draw any firm conclusions from his primary rival’s internal poll.

“Any poll that has an overwhelming majority of respondents saying ‘unsure’ indicates nothing except uncertainty and is inconclusive at best and detrimentally misleading to voters at worst. It is deceitful and could cause suppression in voters,”” said Howard Chou, a former vice chairman of the Colorado Democratic Party who boasts decades of experience overseeing political polls and market research. “While not being able to access the actual data for this latest hypothetical general election race, this is more a poll that only shows the current partisan line support and underscores the unpredictability of this race.”

Boebert and former talk radio host Deborah Flora have qualified for the GOP primary by petition. In addition to Sonnenberg, the other Republicans vying for a spot on the primary ballot are state Reps. Mike Lynch of Wellington and Richard Holtorf of Akron, former state Sen. Ted Harvey of Highlands Ranch, business consultant and former 2nd Congressional District GOP nominee Peter Yu, former top congressional aide Chris Phelen and Hispanic Energy Alliance chairman Floyd Trujillo.

Boebert held a wide fundraising advantage over the other GOP candidates for Buck’s seat at the beginning of the year, finishing the quarter that ended Dec. 31 with $1.3 million cash on hand – roughly 10 times as much as her nearest competitor. The most recent fundraising period ended Sunday at midnight, with reports due to the Federal Election Commission on April 15.

Editor’s note: This developing story has been updated.