There are three issues for which American presidents will always—despite campaign promises, previous votes, and party positions—go their own way:
Trade, energy, and security.
Presidents will always seek expanded trade agreements, greater access to energy resources, and whatever is necessary to secure what we now, alas, call the Homeland.
Democrats and Republicans will vary in how they go about this business—Dems may talk more about renewables and Republicans may project a greater hawkishness—but in the end, each of them, as president, will sign the trade deals, drill for oil and gas, and sop up every last bit of information flowing through the leaky pipes of cyberspace, all to “strengthen America”.
This cuts across interests in both parties. Environmentalists and labor activists will get screwed by Dems on energy and trade, perhaps placated with a few wilderness set-asides or anodyne words in trade deals; hawks and nativists will be unsatisfied by Republicans daunted by popular opposition to extended wars and willingness to open borders to both people and products, respectively; and (civil) libertarians will be screwed by presidents of both parties when it comes to the ever-expanding national security state.
Thus, the more ideologically-minded partisans on either side of the divide will be forsaken again and again, the everlasting Charlie to President Lucy.
As one of those ideologically-minded partisans, I have some sympathy for those who want to believe that this time, this time things will be different, and who disillusioned when they are not.
But as a fan of Machiavelli, I think it is better for us not to have illusions about power.
The promises are nice–necessary, even, to move us to canvass and call and get out the vote—but they go only so far as politics will allow them.
And on trade, energy, and security, that ain’t very far.