Republican Sen. Dean Heller has reportedly raised around $820,000 over the last three months of 2017 for his reelection campaign, approximately half of what his likely Democratic opponent, Rep. Jacky Rosen, raised over that time period.

Heller, widely considered one of the most endangered incumbent senators on the ballot in 2018, also has around $4.2 million in available campaign funds, according to a tweet by Politico reporter Kevin Robillard.

Heller's fundraising leaves his available cash on hand at a similar level to what it was at the end of September, when the Republican reported raising $1.17 million in the Federal Election Commission's 3rd Quarter (July through September) for campaign finance reports.

Heller's primary opponent, businessman Danny Tarkanian, reported raising $310,000 in the third reporting period of the year and hasn't yet released his fundraising total for the latest quarter, but has boasted on social media of a recent fundraiser in southern California netting the campaign more than $200,000.

Rosen reported raising $1.56 million over the last three months of 2017, ending the year with $1.8 million in available cash.

In Nevada's 2016 U.S. Senate race, former Republican Rep. Joe Heck reported raising $1.21 million in the last quarter of 2015 for his Senate bid, while Democrat Catherine Cortez Masto took in $1.308 million over the same time period.

Nevada's primary election is scheduled for June 12, 2018.