A lot of the time, the left can reasonably argue that their increases in the size of government are made out of concern for the common man. For example, they argue that government needs to massively expand its involvement in health care to help the poor get better treatment. I think they are wrong, but that's a different story.
But there are occasionally important litmus tests where the left must decide between the interests of government (and its expansion) and the interests of the common man. I think the DC school voucher program is such an occasion, and its pretty clear that the Democrats in Congress are landing on the side of government. No matter than most Democrats in Congress send their kids to private schools rather than DC public schools. No matter that our new Secretary of Education was unable run a public school in Chicago that our current President was willing to send his kids to.
I think proponents of school choice have been very smart in creating school voucher programs that preferentially target poor kids in failing schools. It eliminates the typical class warfare argument that the program is just about giving rich people a break on their private school tuitions. Democrats are forced to declare on whether the well-being and education of kids in a program that is dominated by poor African-Americans is more or less important to them than sealing a crack in the government education monopoly.