Want to raise the blood pressure of a moderate Republican? Just talk about those on the political right who expect 100 percent adherence to what are generally accepted to be conservative principles. Moderate Republicans prickle at the thought of the conservative base demanding that GOP leaders and candidates agree with them on every issue. In fact, the topic often sparks off-the-record remarks that are decidedly immoderate.

To an extent, moderates have good reason to shake their fists at the base’s demand for purity. There are complex issues which, in all honesty, come down to judgment calls. Even more prevalent are specific political circumstances under which sticking to the so-called principled position could lead to consequences the conservative base would find even more detestable than moderate alternatives.

Yet, the antipathy moderate Republicans express over the conservative right’s demand for purity appears to be more emotional than analytical. This must be so because, at least regarding the selection of presidential candidates, no group has benefited more than moderate Republicans from the base’s refusal to tolerate anything it considers a violation of conservative principles.

The conservative base was not driven to wrath and outrage because Republicans who claimed to represent conservative principles occasionally drifted away from those principles. It took a tidal wave of wholesale abandonment of those principles by the Republicans to finally spark the political right to activism.

Since its awakening, during the final stage of administration of George W. Bush, the political right has had its share of victories and defeats. But its single most glaring failures have taken place in the GOP presidential selection process. Within that arena, the movement’s quest for a candidate who has represented its views 100 percent of the time has been a handicap.

When it comes to picking the GOP presidential nominee, the political right repeatedly hurts itself by demanding “purity” from candidates in two ways:

1. When it fails to separate habitual offenders from occasional offenders.

2. When it loses perspective regarding the full spectrum of issues by focusing solely on a single hot-button issue that pops up during presidential primaries.

Think ahead a year to February 2016. Chances are pretty good that the field of Republican presidential hopefuls will include a handful of conservatives and two or three moderates. If the recent past provides an indication of how the race for the Republican nomination will play out, the conservative candidates will systematically take pot shots at each other in an effort to emerge as “the conservative choice.”

Those with gubernatorial backgrounds will have to defend every bill they signed and policy they pursued. If there are candidates with Congressional backgrounds in the race, they’ll be attacked over votes they’ve cast. This is where the conservative base’s demand for purity becomes its Achilles heel.

Moderates, who by their very nature are willing to tolerate and in many cases even admire compromises, will sort things out and rally around one candidate. The other moderate candidates will drop out early. Meanwhile, the conservative base — confused and dissatisfied because no one in the field meets their expectations — will be divided. They’ll split their support among the conservative candidates, giving two or three enough encouragement to stay in the race.

With one moderate candidate against two or three conservatives, the moderate will have a tremendous advantage as the primary season progresses. By late spring the conservative base will once again be disappointed with the presumptive Republican Party nominee. Voices from the base will blame party insiders and curse the well-financed GOP establishment. But the real fault will have been within the base itself. Setting standards no candidate’s record can stand up to is the surest way to end up with another moderate atop the ticket.

If conservative litmus tests are applied, they should to be applied at the outset — preferably prior to February. The one chance the political right has to choose the next Republican nominee is to pick its candidate early and stick like glue with him or her. Wavering over revelations emerging in the heat of the race about past votes taken or inconsistent policy positions will lead to defeat.

The insistence on “purity” as regards political principles is a common attitude among both the conservative right and the liberal left. However, on the right it represents a degree of philosophical inconsistency.

The idealism of the liberal left is based on a false premise that there is always a flawless solution. This is why they’ll almost always believe a candidate’s promises that are based on vague, wishful fantasy.

The realism of the conservative right is based on an awareness that — in the real world — there are only trade-offs in which decisions must be made between two or more flawed choices. That’s why they’re more likely to recognize the fallacy of political promises that are too good — and too simplistic — to be true.

Hence we see the quandary with which the political right must wrestle. A distinction has to be made between those willing to stand on principle most of the time and those who habitually betray principle. There is always a best choice, never one that’s perfect.