The presidential election is six months away but Democrats have already poured almost $25 million into key states where the get-out-the-vote ground game could tip the Electoral College in a potentially tight contest. Republicans say they will follow suit in the run-up to the election, but so far have sent just over $1 million to state parties.

The usual suspect states, with big numbers of electoral votes at stake, top the Democrats’ list - Ohio, Florida, and Pennsylvania - but the Democratic National Committee investments also reflect the changing demographic map, with North Carolina, Virginia, Nevada, and Colorado receiving special attention.

New Hampshire, Wisconsin, and Iowa round out the top 10 targets for Democrats, based on national party contributions to their state subsidiaries in recent months. Minnesota, Michigan, and New Mexico are also receiving significant extra funding from the national party.

Restore Our Future, an independent super PAC supporting GOP candidate Mitt Romney, has reserved $4 million in television advertising time for an opening gambit in nine states - Florida, North Carolina, Ohio, Michigan, Iowa, Colorado, Nevada, Virginia, and New Hampshire.

With their early spending, both Republicans and Democrats have indicated where they believe the election will be decided in November, said Larry Sabato, director of the Center for Politics at the University of Virginia.

“They’ve already ruled out about 40 states,’’ Sabato said. “This is the permanent campaign stretching over a few more months.’’

Reports filed with the Federal Election Commission document the two parties’ investments so far. President Obama’s reelection committee has also made significant investments in swing-state party committees as part of a strategy that will put a premium on the fall get-out-the-vote ground game.