Democrat Theresa Greenfield leads Republican U.S. Sen. Joni Ernst by 3 percentage points in a Senate race that appears to be among the most competitive in the country.

With just over six weeks to Election Day, the new Des Moines Register/Mediacom Iowa Poll shows Greenfield leading 45% to 42% among likely voters. Another 3% say they would vote for someone else, 2% say they would not vote in the race and 7% are unsure.

Despite heavy campaigning and millions spent on television ads, the results are largely unchanged since June, when Greenfield led Ernst 46% to 43%.

“I will admit to some skepticism about the numbers that we saw in June because we were so close to the primary and Theresa Greenfield was relatively unknown,” said J. Ann Selzer, president of Selzer & Co., which conducted the poll. “But she is holding her own, and I think that says something about Joni Ernst’s vulnerability.”