Expected democratic presidential nominee Barack Obama apparently reaches a far greater Internet audience than the Republican nominee, John McCain. According to a survey released by Nielsen Netratings, Obama’s website counted 2.3 million unique visitors in June while John McCain’s site was the destination of only 563,000 unique visitors, market research firm Nielsen Netratings said today.

Obama’s campaign also leads in Internet marketing, placing nearly 105.7 million image-based ad impressions during the month versus 8.5 million for McCain. The Republican nominee, however, had a lead in search sponsored links: McCain’s campaign saw 5.4 million sponsored link impressions, while Obama had only 1.8 million.

Among active Web users over the age of 18, 89% are registered to vote, according to Nielsen Online’s @Plan. Registered voters who are Internet users are fairly evenly divided between the two major political parties, with 36%Republicans and 35%Democrats. 17% reported being registered Independents with the balance registered as “other” or “not disclosing an affiliation”.

“The fact that so many Web users are registered to vote suggests that online campaign efforts will drive results at the polls,” said Jon Gibs, vice president, media analytics, Nielsen Online. “Campaigns are no longer dabbling online - we expect a candidate’s Web presence to be an integral part of both campaigns.