Well, Wisconsin does not have 'party registration', so I'm not 'registered' with one or the other.
However, I do consider myself a Republican.
Here's why:
The GOP is pro-gun to neutral.
In the case of those that I vote for, they have all been pro.
The GOP opposes Roe v Wade
Now before I get into this, let me state that my position on this has [b]NOTHING TO DO WITH ABORTION[/b]. [u]It has to do with a bunch of liberal supreme court justices dragging a [b]'constitutional right to privacy'[/b] out of a ficticious [b]penumbra of the 14th Ammendment[/b]!!!!![/u] This is by far the most dangerous USSC decision since the Civil War, as it holds the power (if taken full advantage of) to strike down any prohibitive law on the books today (from drug prohibition, to child porn, etc... There are many 'victimless crimes' that (a) should be crimes, and (b) would not be if this 'right' is pushed to the extreme).
The GOP opposes drug legalization.
This is one issue (combined with Foreign Policy) that will prevent me from ever voting for or affilliating myself with the Libertarian Party. I cannot stand anyone who makes policy on the basis of 'So I can Get High', or any party who's leadership is willing to renounce a legitimate law just because people break it. Surrendering to criminals is unforgivable. And yes, this includes MJ (for any purpose. Even 'medicinal' use will promote abuse. You have no idea how many of my former HS classmates would have developed migranes, arthritis, or whatever had medicinal pot been legal when I was in HS. It's all a crock to be able to legally get high.)...
The current GOP is pro tax-cut.
If you run them out of money, they will have to cut the size of government sooner or later. So cutting taxes is the beginning of an important end.
The GOP supports an active, interventionist foreign policy.
This is my other major bone with Libertarianisim. The US needs to be pro-active (er 'Preemptive') with regard to foreign threats and oppertunities. If a country has something that is usefull to us (from natural resources to common enemies) we should support them. If they are hostile to us, we should destroy their ability to act on that hostility (weather this means an economic embargo/blockade ('sanctions' in UNspeak), air raids, an Iraq-style operation to liberate the people from an anti-American government, or a general unrestricted invasion depends on the situation). What we should NOT do is turtle up inside our borders and wait for someone to kick us in the butt before we respond. This sort of isolationisim cost too many American lives in up to and during WWII (since in WWII and before, we were NEVER ready for any war we found ourselves fighting, but rather developed our weapons and tactics from scratch, under fire), and will cost more if we ever revert to it again (far more than the cost of remaining ready and active).
Other issues:
Opposed to socialized national health care. Our local GOP is anti-mass-transit (Milwaukee politics features the GOP (pro-freeway) vs Mayor Norq and the Dems (pro-life-sized-train-set)), and is actually working to shrink local (county) government.
Also, the Republicans may finally accomplish the long overdue task of unifying federal law enforcement under one singular agency (DHS). It hasn't happened quite yet, but it's the logical progression. No more 'ATF, FBI, DEA, EPA, Customs, US Marshals, Border Patrol (who's job should be given to the Army Reserve/National Guard), etc...', just 'DHS'. And if they fire all the redundant desk jockeys (making DHS field-agent-heavy, without the dead weight that came with so many separate agencies), they will actually SAVE MONEY in the process.... And NO, I am NOT worried about PATRIOT, DHS, or any of the rest being part of some 'vast left wing conspiracy' to take over our country/lives...
So that's why I'm a Republican, and 2 reasons why I'm not (and never will be, even if the AWB is renewed, or whatever) a Libertarian.