Ten Democratic senators are defending their seats in states President Trump won in the 2016 presidential election, and five of those lawmakers are at risk of losing to their Republican opponents, according to a new Axios poll.

Sens. Jon Tester, D-Mont., Joe Manchin, D-W.Va., Claire McCaskill, D-Mo., and Joe Donnelly, D-Ind., are the most vulnerable, and have approval ratings of about 50 percent in their respective states. Trump’s approval in these four states is well above that of these four senators.

Sen. Heidi Heitkamp, D-N.D., also narrowly trails her Republican opponent, and all five are at risk of losing in these states, all of which have Trump approval ratings above 50 percent.

The poll is a reality check of sorts for Democrats, who have designs on taking back the House and Senate this year. Losing five of their own seats would make it much harder for Democrats to tip the balance in the Senate, which is now commanded by Republicans with a narrow 51-49 majority.

In five other states, Democrats have narrow-to-moderate leads — Wisconsin, Michigan, Ohio, Pennsylvania and Florida. Trump's approval rating is below 50 percent in each of those states save Pennsylvania.

Editor's note: This story has been corrected to reflect that Sen. Claire McCaskill represents Missouri, not Mississippi.