Trump ally Sen. Joni Ernst holds on in Iowa, NBC News projects

Sen. Joni Ernst of Iowa, a close ally of President Donald Trump, has held on to her Senate seat, NBC News projects.

The contest was an expensive one, an indicator of its importance to Republicans and Democrats alike. The Democratic challenger, Theresa Greenfield, raised slightly more than $47 million and spent over $43 million. Ernst, meanwhile, raised $23.5 million and spent more $21 million.

With 91 percent of the vote counted, Ernst was leading by 51.7 percent to 45.3 percent.

Ernst thanked her supporters and declared victory on Twitter.

The bellwether race was considered an important indicator of Trump's electoral ...