Democrat Rep. Jacky Rosen handed U.S. Sen. Dean Heller, R-Nev., his first-ever campaign defeat late Tuesday night.

The vulnerable GOP senator made a typically strong showing in Nevada's 15 rural, heavily Republican counties. But he didn't fare nearly as well in the state's major population centers, which both broke for Rosen by double digits after the first batches of ballots were counted.

Results from Tuesday's high-stakes Senate election end one of the nastiest and most expensive campaigns in Nevada's political history.

Heller, the only GOP senator up for re-election in a state carried by Hillary Clinton, was dogged by a series of well-publicized reversals on GOP efforts to repeal and replace Affordable Care Act.

Rosen, the freshman congresswoman from Henderson, looked to paint the vulnerable Senate Republican as a yes man for President Donald Trump. She also repeatedly hammered Heller's positions on immigration, tax reform and divisive U.S. Supreme Court Justice Brett Kavanaugh.

Nevada and Washoe County Election Results: General

Heller responded with attacks of his own, questioning Rosen’s oft-touted business resume, her relative lack of legislative experience and her alleged coziness with California political patrons.

Heller had been written off by some pundits before opening a narrow October lead in many polls. But Rosen bounced back in the final days of the campaign. Most surveys showed her even with Heller by the time polls opened on Election Day.

Heller entered the last weeks of the campaign with some $2.2 million in campaign cash to burn. Rosen, in only her second-ever political campaign, out-fundraised Heller in every quarter since jumping into the race in July 2017. She had less than $800,000 in the bank by mid-October.

That was enough to keep up her relentless assault on Heller's health care record, which polls had shown was one of the top issues on voters' minds heading into Election Day. Heller entered the contest with undefeated election record over his 30-year political career.

U.S. Rep. Mark Amodei, the only other federal candidate up for election on most Northern Nevada ballots, was headed to a fourth full term representing Nevada's lone congressional district by early Wednesday morning.

The Republican incumbent picked up 58 percent of ballots counted in the sprawling, GOP-friendly district. Democratic hopeful Clint Koble, a first-time candidate and former Obama-era appointee to the U.S. Department of Agriculture, collected 42 percent of tallied ballots.