As a Libertarian and a Ron Paul Republican, I rarely vote Republican because I've never met an establishment Republican who wasn't a socialist, a Marxist, a warmonger, a usurper of the Constitution, an enemy of civil liberties and a tax and spend progressive.
That said, there are circumstances where I would hold my nose and vote Republican. The US Senate. Screwed up as America is, one of the few things we have going for us is our sovereignty and while it's constantly under attack by the UN and its treaties that are attempting to impose global totalitarian government, treaties are extremely difficult to get ratified.
A treaty must be ratified by 2/3 of the US Senate and that's a very difficult thing to accomplish.
The Law of the Sea Treaty (LOST), a horrifying nightmare of a treaty that literally puts 70% of the earth's surface under UN control and taxing authority, has been sloshing around un-ratified since the days of Ronald Reagan who opposed it. Clinton attempted to get LOST ratified and failed. Even Bush couldn't get LOST ratified despite several attempts and a Republican controlled Senate from 2003 through 2008. The elites of the Bush Crime Family are extreme advocates for ratifying UN treaties because they are indeed major power brokers in what has been dubbed the New World Order.
Republicans are less likely than the Dems to ratify sovereignty slashing treaties. The Dems, on the other hand, are addicted to sovereignty slashing supranational international bodies like the UN and its treaties. It doesn't mean that all Republicans are supportive of US sovereignty, they aren't, but Republicans are generally far less likely to cede US sovereignty to the UN.
If I lived in a swing state with a tight senate race, I'd definitely be holding my nose and voting Republican unless I knew for certain that the candidate was a UN lover (George Allen in Virginia comes to mind). While I'm a fanatical liberty activist, I'm also a fanatical US sovereignty activist.
Without our sovereignty, we have nothing and no hope whatsoever of solving our problems.
Meanwhile, Obama and the Dems are pushing for ratification of the UN's Small Arms Treaty, a direct assault on American 2nd amendment rights. Yes, the UN and the Dems are fanatical about disarming us and the Republican senators are our best bet when it comes to preserving our sovereignty and constitutional rights (now that's something that really makes me cringe!).
Right now the Senate consists of 51 Democrats, 47 Republicans and 2 Independents (who generally vote with the Dems). Another reason to increase Republican representation in the Senate is Obamacare. The senate has unique rules, specifically its cloture vote of 60 which means that a simple majority doesn't pass a bill. However, there are a few exceptions and one of those exceptions is budget reconciliation. Obamacare taxes can actually be overturned with 51 Senate votes.