2012 Election exit polls showed 38% of voters were Democrats, 32% were Republicans and 29% were Independents. Romney got 7% of the Democrat vote and Obama got 6% of the Republican vote. Independents split 55-45 for Romney.
The latest Gallup Poll on party affiliation showed 46% Democrats or leaning Democrat and 40% Republicans or leaning Republican.
http://www.gallup.com/poll/190421/democrats-increasing-edge-party-affiliation.aspx
realclearpolitics.com provides an average of all the latest polls.
The current average is Clinton: 45%/Trump: 39% arrived at by averaging:
Fox News Clinton 44/Trump 38
Quinnipiac Clinton 42/ Trump 40
ABC-Washington Post Clinton 51/Trump 39
NBC-Wall Street Journal Clinton 46/Trump 41
Rasmussen Reports Clinton 44/Trump 39
Reuters-Ipsos Clinton 44/Trump 34
Economist-You Gov Clinton 43/ Trump 39
CNN-ORC Clinton 47/Trump 42
It is much too early for polling data to really matter.