I'm not currently registered with any political party. However, Democrats tend to get my vote in national politics, and here's why:
Republican inconsistencies.
Sanctity of life makes a lot of sense. However, you can't claim that unless you apply it to all ages. If you are Pro-Life, then you can't also be Pro-Death Penalty. Apparently there is something else going on there. The GOP tries to paint Democrats as killers, but most of the Democrats I know are pretty consistent. They have their own opinions which vary widely, but all agree that the final decision is not one that the government should be making, which leads me to my next point.
MORE Republican inconsistencies.
Small government! Republicans make a huge deal over having smaller government. This makes perfect sense - we want our independence, we want our personal freedoms, we don't want interference in our personal & private lives. Unfortunately, this does not apply to women's healthcare when it comes to abortions and it doesn't apply when 2 consenting adults want to get married. Dems get the nod on this one too. The government is necessary to provide needed services - relief following Hurricane Sandy for example. Not that Dems are solely responsible for the relief (though Obama seems to have done much better than Bush did with Katrina), but the point is that the Democrats are pragmatic and refrained from making blatantly inconsistent claims.
Compassion.
This is something that Republicans seem to lack. They lack it in relation to women - preferring to mandate vaginal probes into people who wish to opt for an abortion. They lack it in relation to immigrants - scapegoating and villainizing people, in some cases allowing police to detain them because they look/act/speak in a certain way. They lack it in relation to the gay community - apparently, religion is great only if they conform to the religious precepts that they approve of. Poor - whether its Romney speaking about the 47% or people on Facebook complaining about the "uneducated masses" tipping the balance in favor of Obama, it seems people who make less money are also of less value.
Trust.
Comparing the two parties, one obviously tries hard to incorporate diversity, while the other speaks a great game while acting incongruently. If the Republican Party really wishes to reach out to a wider swath of the population, then they need to change their policies to incorporate a larger segment of said population. They need to put action behind their words so that people will actually believe them when they say a vote for them will be to their own benefit. Generalizing about how 47% of the population believes they are victims does not really engender trust. Defying science in favor of an ancient text, endorsing creationism over evolution, and backing a few scientific outliers to defy a much stronger argument for the case of climate change - definitely not building trust! Telling women that their bodies can naturally shut off a pregnancy when it is a result of rape, endorsing someone who claims such non-sense, or even refusing to denounce such an offensive statement - again, not building trust! Trust is built by protecting those who cannot protect themselves. Newsflash - rich people can afford lawyers.
Diversity.
This relates to trust. If other people like me haven't found a reason to trust you... ie. you have zero diversity... then there's probably a good reason for it. I found it riotous to listen to Rush Limbaugh the morning following Romney's loss. I recall him lamenting about how the GOP has been reaching out to people of color, rattling off the names of Black and Latino leaders in their party. That's about as backwards thinking as someone saying "I'm not a homophobe - I have a gay friend!" Well whoopdee-doo! We're not looking at the faces you put out front - we're looking at the policies you're supporting, we're looking at the families you're affecting, and... occassionally... we look at your crowds on TV... which definitely do not reflect diversity. Take a look at the crowd at the GOP convention and put it next to a shot of who was at the Democratic convention.
Go ahead and claim any number of reasons why people of color, women, youth, and the gay community sway heavily Democrat - level of education, group think, pandering policies, etc.... The reality is - there are people who sit in the middle, and each election cycle they sit around and think "Who best represents me?". Newsflash - with the way our demographics are changing, unless the GOP evolves, that answer will increasingly be a Democrat politician. In a year where a Republican businessman faced an incumbent Democrat with a poor economy, the GOP better learn something. That something can be one of two things - how to be more inclusive of the electorate, or how to be better losers.