LOUISVILLE, Ky. — Democrat Alison Lundergan Grimes pocketed an endorsement from the Kentucky AFL-CIO on Tuesday, while the longtime Republican senator she wants to unseat was promoting a national right-to-work proposal seen by union leaders back in Kentucky as an effort to undermine organized labor.

The events underscored a clear policy contrast between Senate Minority Leader Mitch McConnell and his leading Democratic challenger with a year left before the 2014 election. McConnell, who is seeking a sixth Senate term, faces a GOP primary challenge from Louisville businessman Matt Bevin.