On Monday, the Virginia General Assembly goes into a special and entirely unnecessary session being held in an attempt to persuade stubborn Republicans in the House of Delegates to go along with expanding Medicaid benefits to 400,000 lower-income Virginians who are caught in a health insurance twilight zone.

The session was forced when 66 out of 67 Republicans in the 100-seat House voted down the expansion, claiming it would be fiscally irresponsible to open the program to so many new people. In the process, they are willing to walk away from $2 billion a year in federal funding while risking a state government shutdown in July.

Why is this happening? Their real goals, of course, are to hold a hard line against President Obama and the Affordable Care Act, which relies heavily on expanded Medicaid to meet its goal of increased access to health care, and to boost like-minded candidates in November’s congressional elections. As for their own reelections, most of them don’t have much to worry about. Virginia’s electoral playing field has been set up through gerrymandered districts to allow as few competitive races as possible. All they have to do is guard their right flanks against a primary challenge, and they’re good to go.

Eventually, time and change will catch up with them. But it may not be soon enough to help the Virginians who need Medicaid.

Make no mistake: Virginia is changing. One indication of this is that the mainstream has come out firmly for Medicaid expansion. This broad-based consortium stretches from liberal advocates for the poor to business-minded Democrats such as Gov. Terry McAuliffe and on to business executives, health-care officials, Chamber of Commerce leaders and Main Street Republicans in the state Senate. Some of the lobbyists working to help pass it include members of the previous Republican administration such as former U.S. representative Thelma Drake and Matt Cobb, a former deputy health secretary.

Still, expansion proponents have bent over backward to seek a compromise, offering an audit of the state’s Medicaid program and suggesting using the federal expansion money to set up a market-based alternative to traditional Medicaid. Republican Sen. William M. Stanley Jr. (Franklin) likened this approach, which has found favor with Republicans in some other states, to putting lipstick on a pig.

Naysaying House Republicans are standing firm even though they represent 32 out of the 50 House districts with the highest share of residents enrolled in Medicaid, according to a study by three University of Mary Washington professors. Recent polls suggest more voters support the expansion than oppose it.

This raises a question. If so many people will benefit from the expansion, and so many others think the state should go ahead with it, why would their representatives prevent it? How can such politicians hope to stay in office?

The answer brings us back to gerrymandering, which, by its nature, protects the status quo and prevents change. Of 100 House of Delegates races in 2013, “only 12 to 14 were competitive,” notes Leigh Middleditch Jr., a Charlottesville lawyer and a founder of the Sorenson Institute for Political Leadership at the University of Virginia.

Both parties have been complicit in creating this problem, but it’s the Republicans who are using the system right now to thwart the evolving views of the people — who are moving away from them.

Voter preferences in Virginia are rapidly shifting from red to purple to blue as new residents pour in from other states and countries. From 2006 to 2012, the number of foreign-born residents of the state increased from 770,000 to 950,000, according to new data from the Weldon Cooper Center at the University of Virginia. Most of these, about 68 percent, live in job-rich and liberal-thinking Northern Virginia. Younger Virginians are also a factor. Millennials are leaving rural areas — the home bases of conservative Republicans — for Northern Virginia and other urban parts of the state.

For an example of how those changes are playing out at the polls, look no further than the Democrats’ sweep of statewide races in November. Or President Obama’s victories in both 2008 and 2012. Or consider gay marriage. In 2006, 57 percent of voters supported a constitutional amendment banning it; by 2013, the number supporting a ban was all the way down to 33 percent.

The changes are bound to reach a tipping point, but little will happen to move the House unless the yoke of gerrymandering is broken. Some are trying to make that come to pass. Bipartisan backers of initiatives such as the Virginia Redistricting Reform Coalition want to end gerrymandering by 2020. Middleditch, a movement leader, says that “it’s going to be difficult and take a lot of money but we have six years to do it.”

That’s awfully late, but at least it would be better than never.

The writer blogs at Bacon’s Rebellion and is a participant in The Post’s Local Blog Network.