If you've tried to go to the McCain website and find out detail  about his policies, you'll know how frustrating it is:  you click on issues, choose an option and get redirected to his fantasy 2013 America after McCain waffle.
But what leapt out to me from that is that he's offering a flat tax rate alternative of 19%, the condition of which is no deductibles.
Where then his $5000 health insurance deduction?
As a side note, going to his website is a huge morale boost for anyone worrying that the GOP & McCain are going to be able to paint Obama as just another ultra liberal Dukakis type candidate and sail through the general on that basis.   What his website confirms is that not for  long will McCain be able to come over as a departure from Bush and a true bipartisan appeal candidate:  McCain's policies are ultra right wing.   They really are.  No way could he get bipartisan support for them.  The Democrats should be able to win this election with  ads showing bridges collapsing, the actual conditions of the poorest schools, good hard working middle class Americans whose economic lives have been shattered through illness...
Check out this analysis from the Brookings & Urban Institute's  Tax Policy Center
http://taxvox.taxpolicycenter.org/blog/_archives/2008/4/17/3644448.html
"Cuts this size would pare government back to levels not seen since the Eisenhower administration."