It's pretty evenly divided and the best you can say is that at a given moment in time, what's perceived to be the agenda is unpopular. See, here's the problem. The "majority of Americans" have no idea what the Republican agenda is and vote on things other than the agenda. They vote on who's the prettiest, who Oprah endorsed, if it's hard to find a good paying job, if groceries are too expensive, etc. and blame the party in power. It also depends on how you present said agenda to the average voter. Let the predominate left leaning media translate the Republican agenda into what they want it to be and the majority of those who listen to them will echo it. Let a wordsmith present the democrat agenda to average people and they won't like it either.
So, no, I don't accept that the "Republican agenda" is unpopular with a majority of Americans, because the "majority of Americans" probably couldn't tell you what it is.