Scott Walker dropped out of the Republican primary race today. Last week, Rick Perry dropped out. Most of my liberal friends on Facebook and Twitter cackled gleefully and made fist-pumping “oh, yeah” noises over each of those. They enjoyed the schadenfreude of watching two people they disliked being humiliated and slinking home with their tails between their legs. They shouldn't have enjoyed it. Walker and Perry dropping out is bad for us.
The more people there are in the primary, and the longer they last, the better it is for us. The worst thing that could happen for us is for all of them to drop out (except, presumably for one. No one running as a Republican would be very good for us). There are two simple points involved. One is financial/economical and the other is sociological.
The money issue is the easiest to explain. Lots of candidates eat up a lot of money. Money spent running against other Republicans in the primaries is money not available to spend running against the Democratic candidate in the general election. I want the big donors to spend it all in the primaries. Walker in particular was positioned to waste a lot of money. He was the Koch brothers' anointed. They have publicly promised to spend almost a billion dollars this cycle to create a government to their liking. The longer he looked viable, the more of that money he would have sucked up. Now they are free to decide whether to spend that billion on another presidential candidate or to spread it around buying as many congressional seats as possible (which is what I would have done from the beginning). Allowing the money to become more focused is bad for us.
The sociological issue is almost as simple. The longer the primaries remain competitive without a clear front runner, the more divided the party is going into the general election. After the convention, they'll need to spend valuable time uniting the party rather than running against our candidate. The sooner someone emerges from the pack as the obvious winner, the sooner they can focus their money and supporters on defeating our candidate. Bringing the party together is a major strategic issue. The longer a party remains divided between viable candidates, the more supporters become dedicated to their candidates. The more they become dedicated to their candidate, the more they begin to see other candidates as the enemy. If the enemy wins, their enthusiasm for supporting them approaches zero. An actual convention battle would guarantee hundreds of thousands of supporters, if not millions, either staying home or voting for third parties in November. In 2008, Obama's greatest challenge wasn't defeating McCain, it was regaining the support of the Clinton bitter-enders.
My conservative/Republican friends seem to understand this calculus far better than my liberal/Democratic friends do. We look at every Republican joining the race as mere entertainment. They look at every Democrat joining the race as bad news for Clinton. We need to learn from them. If Carson and Fiorina keep up with Trump, that's great. If Jeb!, Kaisich, and Cruz stay viable, that's even better. If Jindal and those other guys look viable, that means we've all suffered major head injuries and need someone to get us to the ER as fast as possible.
To summarize: lots of Republicans = good, one Republican = bad.