IN-Sen: Poll shows tight race between incumbent Sen. Joe Donnelly, Republican candidate Mike Braun

A new Gravis Marketing poll shows incumbent Indiana Democratic Sen. Joe Donnelly leading Republican businessman and former Indiana state Rep. Mike Braun by 4 points.

What are the details?

The poll revealed that 44 percent of likely voters support Donnelly, and about 40 percent back Braun.

Libertarian Lucy Brenton polled at about 7 percent, and 10 percent of respondents say they are undecided.

The poll of 377 registered Indiana voters was conducted Oct. 12-16 and has a margin of error of 5.1 percentage points.

Seventy-six percent of respondents say they are "very likely" that they will vote in the upcoming election. Thirteen percent of respondents say they are "likely" to vote in the upcoming election, and 11 percent of respondents say they are "somewhat likely" to vote in the general election.

What else?

A Fox News poll released Oct. 3 showed Donnelly leading Braun by 2 points, and a previous Ipsos Public Affairs poll showed a nearly even split.

Trump officially endorsed Braun in September during a campaign rally in Evansville, Indiana.

The Senate election in Indiana is one of 10 “most likely to flip in 2018,” CNN reported in January. The Cook Political Report calls the race a toss-up, as does Real Clear Politics.

Donnelly and Braun's final debate is set for Oct. 30, and the general election will be Nov. 6.