A new poll of Arkansas Senate race shows Sen. Mark Pryor (D) with a clear lead over Rep. Tom Cotton (R). It's the latest in a string of recent surveys suggesting Pryor may not be as vulnerable as many have considered him in recent months.

A new NBC News/Marist poll released Monday finds Pryor leading Cotton 51 percent to 40 percent among registered voters. In surveys of states with two other battleground Senate races, NBC/Marist found Senate Minority Leader Mitch McConnell (R) running about even with Secretary of State Alison Lundergan Grimes (D) in Kentucky and businessman David Perdue and Rep. Jack Kingston at the head of a crowded pack in the Republican primary for U.S. Senate in Georgia.

President Obama continues to be unpopular in Arkansas. Nearly six in 10 (57 percent) residents disapprove of the job the president is doing while just 33 percent approve. Those who disapprove of the job Obama is doing side strongly with Cotton.

A majority of women (55 percent) back Pryor, while men are split between Pryor and Cotton, with 46 percent supporting each candidate.

For much of 2013, Pryor was seen by many close watchers as the most vulnerable Democratic senator facing reelection in this fall. But recent polls show reasons for fresh Democratic optimism. An April New York Times Upshot/Kaiser Family Foundation survey showed Pryor up 10 points, while other polling has shown a neck-and-neck race.

In Kentucky, McConnell (46 percent)  and Grimes (45 percent) are running about even, the new NBC/Marist poll shows. The Blugrass State is one of Senate Democrats' two best pickup opportunities this cycle.

The other is Georgia, where the race for the Republican nomination remains competitive eight days ahead of the primary, with more than one in five (22 percent) likely Republican voters still undecided. The NBC/Marist poll shows Perdue (23 percent) leading Kingston (18 percent) among Republicans likeliest to vote in the primary. Former secretary of state Karen Handel is third with 14 percent, while Reps. Paul Broun and Phil Gingrey lag behind at 11 percent apiece.

Most observers expect a runoff to be triggered -- which would happen if no candidate secures a majority of the vote next Tuesday. The winner of the GOP nomination will likely face Democrat Michelle Nunn, who the poll shows runs about even with each of the Republican candidates.

A poll conducted for the Atlanta Journal-Constitution released last week showed Nunn leading by at least eight points against Kingston, Broun, Handel and Gingrey. The survey showed her running neck and neck against Perdue. In the NBC/Marist poll, Perdue also performs best among Republicans against Nunn.

Kentucky's primary is also next Tuesday. McConnell is well ahead of GOP challenger, businessman Matt Bevin, leading 57 percent to 25 percent among Republicans likeliest to vote, the new poll shows.

The surveys of all three races were conducted from late April to early May.