Democratic candidates for Senate in the hotly contested states of Missouri and Nevada appear to have the advantage on healthcare headed into the midterm elections, according to a poll released Monday by CNN.

The poll suggests that Democratic messaging is resonating with certain voters. In Missouri, 31 percent of voters called healthcare the most important issue in deciding their vote. In Nevada, 26 percent of voters said it was the most important issue.

Voters who identified healthcare as the issue that will drive their vote are more likely to vote for Democrats, the results show. Missouri Sen. Claire McCaskill, the Democratic incumbent, has a 69 percent to 27 percent lead among this group in her race against Attorney General Josh Hawley. Meanwhile, Rep. Jacky Rosen, a challenger to Republican Sen. Dean Heller, has a 74 percent to 16 percent lead in the same group in Nevada.

Overall, the two races are neck-and-neck. McCaskill is edging out Hawley 47 percent to 44 percent, while Rosen leads Heller 47 percent to 43 percent.

Democrats running for office all over the country have made healthcare a central part of their re-election campaigns, drawing attention to a lawsuit by Republican officials to undo Obamacare and the party's failed repeal efforts in Congress.

Voters who put immigration or the economy at the top of their list of priorities during the midterm are more likely to vote Republican.

The polls were conducted by the market research firm SSRS by phone among 1,003 voters from Sept. 25-29.