Republicans have the edge in two important Senate races in Arkansas and Michigan, according to new polling released Tuesday.

Sen. Mark PryorMark Lunsford PryorMedicaid rollback looms for GOP senators in 2020 Cotton pitches anti-Democrat message to SC delegation Ex-Sen. Kay Hagan joins lobby firm MORE (D-Ark.) trails Rep. Tom CottonThomas (Tom) Bryant CottonProtecting American innovation Russian spy poisoning brings world powers closer to day of reckoning GOP senators see Tillerson ouster as the new normal MORE (R-Ark.) by 48 percent to 41 percent, according to a new poll conducted for the conservative group Citizens United, while former Michigan Secretary of State Terri Lynn Land (R) narrowly leads Rep. Gary PetersGary Charles PetersToyota halts self-driving car tests on public roads Coalition presses Transportation Dept. for stricter oversight of driverless cars Warren turns focus to Kushner’s loans MORE (D-Mich.) by 42 percent to 40 percent in a poll from Democratic firm Public Policy Polling.

Most polling has found tight races in both states, though Democrats appear to be in better shape in Michigan since neither Peters nor Cotton are that well known yet statewide.

President Obama isn't in great shape in either state, though his standing in both polls hasn't slipped as bad as he has nationally. His approval rating in Arkansas is at 35 percent with 61 disapproving, just a slight dip from the 37 percent he won in Arkansas last year. In Michigan, his approval rating is at 47 percent, with 51 percent disapproving — that's down from the 54 percent of the vote he won there in 2012.

Pryor's own approval ratings aren't that bad — 44 percent of voters still approve of the job he's doing, with 39 percent disapproving.

Partisan polling should always be taken with a grain of salt — especially when it's released by a group backing one candidate, and Citizens United is a Cotton supporter. But both polls show Democrats are going to have to fight hard to hold control of the Senate. Arkansas is a must-win for the GOP this election cycle, while Michigan is one of a handful of states where they hope to expand the Senate map.

Citizens United's poll of 400 likely voters was conducted by GOP pollster Kellyanne Conway from Dec. 6-7 and has a margin of error of plus or minus 4.9 percent.