How cool would it be if you served two different colors of martinis, red and blue, to your Democrat and Republican friends? (OK, assuming you think the idea is cute and not something from Martha Stewart's reject pile, and assuming you actually have any Republican friends.) Here's how to do it:
The red martini is simple; it's called a cosmopolitan. Cosmo's, as they're affectionately called, are usually made with two parts vodka to one part Cointreau or triple sec (both orange flavored), and two to three parts cranberry juice. They're garnished with lemon or lime. There are zillions of possible variations on this theme. You can choose a flavored vodka, like Absolut Mandarin, Sky Citrus or any of the many that are out there now.
Don't get too crazy with your vodka flavor because it also has to pair well with cranberry juice. Also, if you use a fancy triple sec then you won't want to mess with any flavored vodka. Cointreau and Curaçao (koo-rah-SOW, rhymes with how) are two kinds of higher-quality triple-distilled orange liqueurs. If you use Cointreau for the citrus flavor, you'll want to keep your other ingredients simple. It's expensive, though, so if you want to go cheap and fun, then experiment, with cran-raspberry, cran-peach or any other red juice. Your conservative friends (or the lefties you've drafted into impersonating them for the purpose of your cocktail party) will love it. Whatever you choose, shake with ice, pour into glasses and garnish with an orange wedge.
For your Democrat guests, you can make blue martinis using blue Curaçao. Curaçao is named for the Caribbean island where the bitter oranges used to make this stuff are grown. It comes in blue and sometimes other colors. You can make a blue martini using vodka, or better yet, gin. Don't be afraid of gin. Especially when mixed with a healthy dose of Curaçao, it's tasty, not scary. Use three parts good-quality gin to one part dry vermouth and one part blue Curaçao. Shake with ice and pour into martini glasses. If people really whine, you can use vodka for these, too. Garnish with an orange wedge and serve.
As you get drunker, you'll get more creative with your recipes. Go for it! As your guests get drunker, they'll care less about how bad their drinks are.