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.

If Brown wins, it could expand Republicans' likely majority in the U.S. Senate. If Rosen wins, it could make controversial bills harder to pass.

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.