Nevada Democrat Jacky Rosen is in a neck-and-neck battle in her bid to return to the U.S. Senate for a second term, while her party lost its slim voting majority in the upper chamber of Congress.

Democratic Sen. Jacky Rosen trailed Republican Sam Brown by less than 1,000 votes as Nevada counties stopped reporting results early Wednesday morning. As of Wednesday at 3 a.m., Brown led Rosen by 870 votes — or 0.

The two major candidates for Nevada's U.S. Senate seat cast their ballots Tuesday morning as close attention is paid to which party will control the Congression

A Republican group supporting Senate races says it will spend $6.2 million on TV, radio and digital ads beginning this weekend.

This would be considered a major upset. Polls and election forecasts had Jacky Rosen leading Sam Brown strongly throughout the entire campaign.