It is not the case that half the country works for the team D and half the country works for team R. We can debate a bit about how much getting team D elected is important relative to other kinds of political activism, but you can't control people. If you're a politician, such as an about to be retired one whose name rhymes with Laire McBaskill, you cannot expect to control "The Left." It's your job to get 50%+1 people in your relevant geographic area to vote for you, and you can't get mad because some dumb liberal said something on TV, or because pro-choice activists had other things to worry about than getting you elected, etc. You don't have to love this stuff, but you have no power to change it. It's your job to figure out how to get elected in the world you live in, not the world you want to live in.
Dumb liberals are dumb, fine, and they don't understand the struggles of a rich politician in Missouri, fine, but, dumb liberals don't work for you and if it's so important that they shut up then "making dumb liberals like you" should be a concern. You can't shut them up by yelling at them.
Generally, "centrist" Dems in red states can lecture about winning elections in red states all they want (though such rules do not apply in, you know, blue states) as long as they actually win elections. When they lose them they get to shut up about how it's everybody else's fault, particular when it's the fault of random voters. It isn't as if Dem leadership was forcing tough votes on these people all of the time, because Paul and Mitch have been in charge of such things.
I'm no highly paid political consultant, but I suspect that what swing and non-voters want in red states is not a 1995-era centrist Democrat, even if they don't want full communism like I do. "What voters in the heartland want is best articulated by Richard Cohen and Fred Hiatt" has always been a rather strange approach to politics.
