The Virginia House of Delegates could move Friday to adopt a stricter criteria for ensuring that each of the state’s 100 legislative districts is similarly sized than it did 10 years ago, when the General Assembly last realigned its legislative maps in response to the once-a-decade census.

The Constitution requires that districts be roughly the same size, to ensure that everyone’s vote counts equally. That is why district lines must be redrawn every 10 years, after the release of the census, to ensure that districts take into account population growth and shifts.

Courts have held that congressional districts must be practically identical in size.

State and local districts, courts have said, can vary a bit more. They’ve ruled that if you divide a state’s population exactly evenly, state and local districts can be as much as 5 percent bigger or 5 percent smaller than that ideal size.

When Virginia last drew its maps in 2001, the House and Senate each agreed they’d be stricter — to help ensure that their maps stood up to judicial scrutiny in case of a lawsuit, and to better adhere to the one man, one vote principle. They made sure that each of the state’s 40 Senate districts and 100 House districts was no more than 2 percent bigger or 2 percent smaller than the ideal.

Thursday, each chamber submitted resolutions that will guide their redistricting work and be considered by their respective Privileges and Elections Committees at meetings Friday. The Senate, like in 2001, has proposed the same 2 percent number.

But the House has proposed allowing districts this year to vary from the ideal size by no more than 1 percent.

Would that make a difference in the process? Absolutely.

According to the 2010 Census, the House will be aiming to draw districts so that each contains 80,010 people. That’s the ideal size. If they agreed to a 2 percent variance, it’d mean that districts could have as many 81,610 people or as as few as 78,410.

By adopting a 1 percent guideline, their margin for error shrinks: They’d be agreeing that districts could contain no more than 80,810 people and no fewer than 79,210.

Those are significant differences when trying to draw districts that keep cities, counties, even precincts and neighborhoods together.

“It’s to try to keep the districts as closely balanced, population-wise, as possible,” said Del. Mark Cole (R-Fredericksburg), chairman of the House’s Privileges and Elections committee, explaining the proposal.

But, Cole said, there’s a downside to selecting the 1 percent variance.

“Whenever you select a tighter population criteria, then that gives you a little less flexibility in where you can draw the lines,” he said. “There’s a trade-off — and we’ll debate it tomorrow.”

Cole said the committee could alter the proposal at its meeting Friday.

State Sen. Janet D. Howell (D-Fairfax), chairwoman of the senate’s Privileges and Elections committee, said she was only alerted Thursday to the House shift.

“It’s going to be harder for them to keep communities of interest together,” she said.

They’ll be adopting their criteria, just as we'll adopt ours,” she added. “We decided to go with the same as we used 10 years ago — it seemed like a feasible number and it’s one that’s already been litigated.”