LAS VEGAS (AP) — Nevada Sen. Dean Heller has $4.2 million in his campaign fundraising account as the Republican prepares to fend off a primary challenge and Democrats hoping to turn his seat blue next year, according to fundraising reports filed Monday.

Heller, viewed as one of the Senate's most vulnerable Republican incumbents for 2018, raised $1.1 million from July through September, pushing his account total over $4 million.

The senator is considered at risk of losing next year partly because he's the only one up for re-election in a state President Donald Trump failed to carry last year.

Freshman Democratic Rep. Jacky Rosen announced earlier this year she's seeking Heller's seat, and Republican businessman Danny Tarkanian says he plans to challenge Heller in the GOP primary.

Tarkanian's most recent fundraising report was not yet posted with the FEC by midday Monday, the Las Vegas Review-Journal reported .

Rosen reported raising $1.2 million, leaving her with the same amount in her campaign account.

She announced her challenge of the senator in July, calling Heller an "enabler" of Trump.

Heller refused to endorse Trump for president and has clashed with him publicly over health care. He already was expecting a tough race for re-election in 2018 and now must survive a primary challenge from Tarkanian that will exacerbate fractures in the GOP.

Tarkanian, the son of former UNLV basketball coach Jerry Tarkanian, won an endorsement from former Alaska Gov. Sarah Palin. He has said he will join with Texas Sen. Ted Cruz, Utah Sen. Mike Lee and Kentucky Sen. Rand Paul to fight "for real reforms against the liberals in our party."

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Information from: Las Vegas Review-Journal, http://www.lvrj.com