The Democratic Congressional Campaign Committee is running a television spot for one week on CNN and MSNBC. The ad says "Paul Ryan and establishment Republicans" will "never stop" trying to repeal existing health insurance benefits.
Party leaders say their polling shows Ryan and the GOP Congress have lost popularity because of their health care proposals.
The campaign group has bought three weeks of radio ads in 11 Republican House districts. Those ads don't mention Ryan and instead name the local member of Congress.
Democrats are trying to flip at least 24 GOP-held seats to reclaim a House majority in 2018.