Two GOP polls released Monday show a tight race for Senate between Sen. Mary L. Landrieu, D-La., and her Republican challenger, Louisiana Rep. Bill Cassidy.

The Senate contest is expected to be one of the closest of the cycle. National Republicans are targeting the state, and the Senate GOP’s campaign arm recently released its first advertisements of the cycle there.

Landrieu leads Cassidy, 45 percent to 41 percent, according to a new poll conducted by OnMessage Inc. for the National Republican Senatorial Committee. The live interview poll surveyed 600 likely voters between Aug. 13 and Aug. 15 and had a margin of error of 4 points.

Also, a new automated survey from Harper Polling/Conservative Intel showed Cassidy leading Landrieu, 47 percent to 45 percent, within the 4-point margin of error. The same poll showed Landrieu leading a lesser-known GOP candidate in the race, Rob Maness, 47 percent to 41 percent. The Harper Polling/Conservative Intel poll surveyed 596 likely voters from Aug. 14 to Aug. 15.

It’s worth noting that no candidate received 50 percent or more in either of these polls. If that happens on Election Day in Louisiana, the race would continue to a December 2014 runoff between the top two vote recipients regardless of party.

The Louisiana Senate contest is rated a Pure Tossup by Rothenberg Political Report/Roll Call.