One of the reasons that John McCain is unlikely to win this election is that he has no coherent or realistic plan for actually accomplishing anything that he is proposing. (In addition to that, his ideas aren't all that popular with most people, but that is another subject.) Somebody should press John McCain about how he expects to get any of his proposals passed into law given that the Congress will most likely be overwhelmingly Democratic. McCain would no doubt give his usual answer about how he has a history of reaching out to the opposition party to pass campaign finance reform and reach agreement on other issues, but since his move to the right over the last few years in preparation for running for president, he has a lot less ability to do that. John McCain was never even that popular in his own party, and would face hostility from both sides of the aisle given the divisive nature of his campaign.
So McCain can talk all he wants about not raising taxes on the rich, but the reality is that the Bush tax cuts expire next year, and he would need a majority of the Congress to vote to extend them. That would not be likely to happen. McCain can talk about his plan to move health care away from an employer-based system, to some kind of partially-subsidized individual system, but a majority of Congress is never going to pass any such thing. McCain can talk about staying the course in Iraq, but even the government of Iraq is not going to agree to a permanent US presence in that country, and Congress would not fund it.
We focus so much on the Presidential race, and neglect the importance of Congress, that we forget that the President does not really control the government, especially on domestic issues, unless he has substantial support in Congress. In most democracies in the world, the government cannot even function at all unless they can assemble a working parliamentary majority. Our government is designed to operate even if the Congress and President are from different parties, but it certainly doesn't produce the results that the President wants if the Congress is hostile.
So while McCain tries to scare people by raising the spectre of an unholy Obama-Pelosi-Reid troika, the reality is that a Democratic-controlled Congress and Executive branch will actually be able to put a coherent program into place; while on the other hand a McCain led government is a recipe for gridlock. McCain cannot promise anything better than that.