Voters in general, and Christian voters in particular, express frustration with the lack of principle that characterizes most politicians, and the "flip flops" they engage in during election campaigns. Yet without winking at the lack of principles, it might help us to understand, and perhaps be a bit more forgiving, if we understand that the institutions of democracy themselves---and of U.S. democracy in particular---create incentives for politicians to behave the way they do. Some of these incentives can be changed; others most will not want to change, even if it would promise a change in the behavior of politicians.
Americans sometimes forget that the U.S. presidential election is not one election, but many. Not only do voters elect delegates to nominating conventions on a state-by-state basis, but the election to the presidency occurs through the Electoral College---chosen on a state-by-state basis rather than by a majority of the popular vote.
Politicians need to win what political scientists call the "pivotal" voter in order to be elected to office. In two-party majoritarian elections with a voters distributed along a regular "left-right" continuum, politicians must win the vote of the median voter. So their policy positions will tend to cluster around the policy preferences of the middle voter.
Why the Median Voter Matters
Consider the effect of the primary system on the policy positions that election-oriented politicians take. The median Republican voter in any state tends to be more conservative than the median Democratic voter in that state. In their respective primary campaigns, Republican and Democratic politicians (again, with exceptions) have an incentive to position themselves to appeal to their party's median party voter. After all, they will not be their parties' nominee unless they win their respective primary campaign.
Because election-oriented politicians have an incentive to appeal to the median voter in their respective primaries, "closed-party" primaries---in which only registered party members vote---tend to pull the positions of Republican and Democratic politicians apart.
But all voters subsequently mix together for the general election. That means the median general-election voter in each state is more conservative than the median Democratic-primary voter, and more liberal than the median Republican-primary voter. This, in turn, means that the respective winners of the parties' primary campaigns have articulated policy preferences during the primary that turn out to be "too extreme" for the median voter in the general election.
This creates incentives for candidates to "rush to the middle," that is, to become more centrist, for general elections. This does not mean that candidates are pandering to party regulars any more than it means that they're pandering to moderate voters. The behavior, as it were, is incentivized by the institutional structure of the democratic selection process in the United States.
Noting that, however, does not imply that "rushing to the middle" is never costly for politicians. Candidates develop reputations based on what they say during primary campaigns. Moving too fast or too far toward the middle during the general-election campaign may risk losing a candidate's partisan supporters. Or if a candidate articulates a new policy position, the median voter in the general election may not believe a candidate's new, more moderate positions in a general election campaign.
Significance of a Candidate's Reputation
The importance of reputation can be seen in the re-election failure of the first President Bush. In his first general election campaign for president, Bush staked out a clear policy position on taxes: "Read my lips: No new taxes." He subsequently raised taxes during his first administration, and subsequently lost to Bill Clinton when he ran for re-election.
I've heard President Bush address this topic numerous times in his post-presidency speeches. He still argues that he needed to compromise with the Democrats over taxes in order to get Congress to move on reducing the budget deficit.
That may be correct. But what Bush still seems to miss is that his "no new taxes" position wasn't simply one policy position among many. It was his signature policy position in that campaign. As a result, keeping that policy commitment became a character issue for Bush; his reputation hinged on it. When he compromised with the Democrats to reduce the deficit by increasing taxes (and cutting spending), he set up the loss of his subsequent election to Clinton, in part, because those who supported him in the first election no longer trusted his words.
Nonetheless, many of Bush's supporters also continued to support Bush. Like the candidates, many voters understand that majoritarian politics means that you get the policies you prefer only if your candidate actually wins. Ideological purity may be emotionally satisfying, but it typically doesn't win a lot of elections. The institutional structure of democracy sets up the incentive for many voters to accept the "flip flops" of their candidates, as well as setting up the incentives for the candidates to flip flop in the first instance.
Christians and Political Realism
Again, I do not mean to suggest that politicians should not be held to their words. Nonetheless, understanding the incentive structure that politicians face helps Christians and others to have realistic expectations about what politicians "do" do, as opposed to what the "should" do. And in so doing make sounder judgments in expectation that candidates will moderate their positions.