Maryland voters would cast ballots in the 2012 presidential primary election in April and the 2014 gubernatorial primary would move from September to June, under legislation moving through the General Assembly.

In 2008, Maryland, Virginia and the District all held primaries on Feb. 12, creating a Potomac Primary that gave the region greater importance in the competitive race.

Senate President Thomas V. Mike Miller Jr. (D-Calvert) said he doesn’t like the date change, but noted that the scheduling of elections is being driven by the national political parties.

“It makes no sense that New Hampshire and Iowa drive the politics,” Miller said, referring to party rules that protect the first-in-the-nation nominating contests in those states, held in February.

If Maryland’s primary elections are not tied to those in neighboring states such as Virginia or Pennsylvania, Miller said, “It means we’ll see fewer candidates and lower turnout.”

Virginia lawmakers approved legislation last month to hold the state’s primary elections on March 6.

The legislation, approved by the House of Delegates on Monday and sponsored by the administration of Gov. Martin O’Malley (D), also would move the gubernatorial primary from the second Tuesday in September to the last Tuesday in June.

The bill is partly a response to a federal law passed in 2009 designed to ensure that military and overseas voters have sufficient time to receive absentee ballots and participate in elections.

Moving the primary to June in gubernatorial years would be a major change in Maryland politics — effectively extending the general election campaign by a few months.

“It gives everybody a chance to regroup after the primary,” said House Speaker Michael E. Busch (D-Anne Arundel), who said the greatest impact would be on statewide races like governor and U.S. Senate.

Busch said in deciding when to hold the primary in gubernatorial years, there was a sense that the summer vacation season would hurt voter turnout.

“July and August didn’t make any sense,” he said.

May was ruled out, Busch said, because many local officials who will appear on the ballot are still working on budget issues for their jurisdictions.

The Senate is expected to amend a similar bill to reflect the provisions of the House version Friday, according to an aide to the Senate president.

Staff writer Rosalind S. Helderman contributed to this report.