Iowa is where it all started for President Obama. It's where he won twice in a general election. But he's no longer Mr. Popular there.

Obama's average approval rating in Iowa was 38 percent during the first half of the year, according to new data from Gallup, five percentage points below his national average. Since notching a second straight win there in 2012, Obama's numbers have gone steadily downhill, as the following Gallup chart shows.

It's a remarkable dip in a state where Obama's 2008 caucus win helped propel him past Hillary Clinton in a historic primary campaign. What's also notable is that throughout his first term, Obama's numbers in Iowa were mostly stronger than they were nationwide. That hasn't been the case in his second term.

Obama won Iowa by about nine points in 2008 and nearly six points in 2012. He won the 2008 caucuses by about nine points.

For context, Obama's numbers have been dropping all across the country, and what we're seeing in Iowa is part of a broader trend. You don't get an approval rating in the low 40s without support dropping for you practically everywhere. Even in California, a heavily Democratic state, Obama's approval rating was just 45 percent, according to a recent survey.

So, what does this all mean in 2014? It's bad news for Rep. Bruce Braley, the Democratic nominee for Senate in Iowa. Braley is in a close race against Republican Joni Ernst. The contest is shaping up as a key piece in the battle for the Senate majority.

While the president's approval rating is hardly the only determining factor in a statewide contest, it can be a significant one. And in Iowa, Obama has gone from Democratic asset to albatross.