MANCHESTER, N.H. -- Arizona Sen. John McCain lashed out at Mitt Romney Saturday in a speech before a meeting of the New Hampshire Republican Party, suggesting that the former Massachusetts governor was trying to conceal his imperfect conservative record and perhaps even "con" Republican voters.

"You might not always agree with me on every issue, but I hope you know I'm not going to con you," McCain said, after attacking Romney's record as a conservative for several minutes. The new assault from McCain comes at a time when Romney and former New York Mayor Rudy Giuliani have been trading public snipes in an effort to identify themselves as the two principal choices in the Republican Party.

In a speech in Nevada on Friday, Romney attacked Giuliani's opposition to the line-item veto. "I believe conservatives across the nation and particularly in states where I have been able to take my message, like Iowa and New Hampshire and South Carolina and Michigan and Florida and Nevada, that conservatives that have heard me time and again recognize that I do speak for the Republican wing of the Republican Party," Romney told the Nevada gathering, according to the Associated Press.

Less than 24 hours later, McCain responded with a blistering and detailed assault on Romney that read like an opposition research paper. "I don't usually do this but I'm going to depart for a moment from the issues I want to talk to you about today," McCain said at the beginning of his address to the party meeting. "One of the other Republican candidates made an extraordinary statement yesterday. Former Gov. Romney yesterday proclaimed himself the only real Republican in this race. As we all know, when he ran for office in Massachusetts being a Republican wasn't much of a priority for him. In fact, when he ran against Ted Kennedy, he said he didn't want to return to the days of Reagan-Bush. I always thought Ronald Reagan was a real Republican. When Gov. Romney donated money to a Democratic candidate in New Hampshire, I don't think he was speaking for Republicans. When he voted for a Democratic candidate for president, Paul Tsongas, I don't think he was speaking for Republicans. When he refused to endorse the Contract With America, I don't think he was speaking for Republicans. And when he was embracing the Democratic position on many major issues of the day, I don't think he was speaking for Republicans."

"So you'll understand why I'm a little perplexed," McCain continued, "when Mitt Romney now suggests that he's a better Republican than me, or that he speaks for the Republican wing of the Republican Party. I think I've gotten to know the people of New Hampshire pretty well. I know that before I can win your vote, I have to win your respect. And to do that, you expect me to be honest with you about what I believe. You might not always agree with me on every issue, but I hope you know I'm not going to con you. The most important thing we have in this life is our self-respect. And I'm not going to trade mine for anyone's vote or for any office. I'm going to tell you what I believe and let the chips fall where they will."

Afterward, in a gaggle with reporters, McCain was asked if he was directly accusing Romney of trying to "con" Republicans. "No, but it's very clear that he has changed positions on almost every major issue in his various campaigns," McCain said.

In an e-mail response, Romney spokesman Kevin Madden attacked McCain for his support of the McCain-Feingold law (Romney previously endorsed a different set of campaign finance reforms), McCain's previous opposition to President Bush's tax cuts (McCain now supports them) and McCain's opposition to a constitutional amendment to ban gay marriage.

"While the others are opposed to a Federal Marriage Amendment to protect traditional marriage, Governor Romney has strongly supported it. Governor Romney's strong record of bringing about conservative change is what sets him apart from the other candidates," Madden wrote. "Senator McCain's signature legislative accomplishment, the McCain-Feingold campaign finance reform bill, is a legislative abomination that we happen to disagree with, along with many other conservatives. The McCain-Kennedy immigration legislation he championed was exactly the wrong approach and only encouraged law-breaking and borders that are less secure. Lastly, Senator McCain's vote against the Bush tax cuts that helped grow our national economy showed conservatives that he is not a friend of the pro-growth economic policies that put more money back into taxpayers' pockets. Senator McCain's joining with Democrats to vote against those tax cuts was bad policy. Governor Romney supports extending those tax cuts."

Stay tuned. It is only just beginning.