“Today we achieved something amazing — 2,000,000 donors owning a piece of this campaign,” a message on Obama’s contribution page reads. “In the face of [Republican presidential candidate] John McCain’s low road tactics, it’s more important than ever to keep our movement growing and show the power of millions of grassroots supporters coming together to work for change.”

While Obama has opted out of public financing for the general election and can continue to raise money after accepting the nomination, Sen. McCain (R-Ariz.) has to make his final fundraising push now. McCain will accept public funding, and the restrictions that come with it, and receive $84 million for the general election after he accepts the nomination.

The GOP standard-bearer sent a fundraising email to supporters shortly after Obama’s announcement, urging donations and hitting the Democrat for reversing on his commitment to accept public funds. 

“I intend to keep my promise of accepting federal funds for the general election,” the Arizona senator wrote to supporters. “Sen. Obama has chosen to break the promise he made many times before and will opt out of accepting these funds. I am a man of my word and I intend to honor the promises I have made during this campaign.”

McCain also launched a thinly veiled attack on Obama’s patriotism, echoing a similar line used by surrogates of his campaign.

“My friends, I have made many promises during this campaign — promises I intend to keep. First and foremost, I promise to put our country first, before my own self-interest. I have put my country first throughout my entire life. I owe America more than she has ever owed me.”

Earlier this week, during a campaign stop in Pennsylvania, McCain ally Sen. Joe Lieberman (I-Conn.) suggested that Obama has not always put his country first.

Passing 2 million donors is a significant benchmark for the Obama campaign, which has been able to utilize online fundraising tools on a scale previously unseen.

The Illinois Democrat raised a total of $340 million through the end of June, much of it coming in small-dollar contributions online. Obama has spent $267 million during the cycle and had $71 million in cash on hand, according to most recent Federal Election Commission filings.

McCain has raised $145 million total, and had $35 million at his disposal coming into July.