The ability of presidential candidates to affect either the outcome of the election or even influence the substantive policies that make up his or her party’s platform is a lot more limited than pundits often believe. A lot of time, the best a party can hope for from a candidate is that he or she doesn’t taint voters’ deliberations over which party to choose.

For instance, Ross Douthat’s column today begs for better GOP candidates, and warns of the dire consequences if they nominate a bland placeholder who isn’t fundamentally serious about dramatic change — citing Bob Dole’s nomination and subsequent loss to Bill Clinton in 1996.

He’s doubly wrong.

First of all, Bob Dole (like Walter Mondale in 1984) gets a bad rap. The economic indicators and other fundamentals predicted that Bill Clinton would win comfortably; the truth is that Dole’s campaign probably didn’t make it any worse, which was the real danger for the GOP. Clinton got his solid win, but was denied a landslide with coattails.

Movement conservatives blame Dole for running an insufficiently radical campaign, and worry that the same thing will happen again. But the reason Dole ran away from the Gingrich “revolution” at the time was that it had already died in the winter of 1995-1996. People just didn’t want “conservatives to reimagine government’s role” (in Douthat’s words) if it meant slashing Medicare and Medicaid. To interpret the 2010 landslide — in which Republicans campaigned against Democratic cuts in Medicare — as some sort of mandate to radically change those programs, despite polling that shows very little support for that position, is to commit the same mistake that the Gingrich revolutionaries made in 1995.

We’re in the middle of the first of three promised showdowns over the budget and the debt limit that will all be resolved, one way or another, by 2011 or early 2012. The outcomes of those conflicts will determine what issues Republican presidential candidates believe are sensible to run on. It’s certainly possible that Paul Ryan and others are correct that this time, the public really does want radical change; if that comes to pass, twelve months from now, Romney or Palenty or Barbour or whoever will be running on ending Medicare as we know it. More likely, Barack Obama will be perceived the winner of the budget showdowns, and House Republicans (like the GOP governors pushing through radical cuts) will wind up unpopular.

If that’s the case, the nominee — unless it’s Newt, Michele Bachmann or the Sage of Wasilla — will most likely keep his or her distance from House Republicans. Just like Bob Dole did.