“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.”

Romney’s campaign fired back, also focusing on McCain’s past actions.

“Governor Romney is the candidate in this race best prepared to represent the principles most important to Republican voters,” said Romney spokesman Kevin Madden. “He has articulated a comprehensive vision for a strong economy, a strong military and strong families. We can’t have a nominee who only wants to talk about two issue platforms instead of all three.”

Madden attacked McCain’s signature campaign finance bill, calling it “a legislative abomination that we happen to disagree with, along with many other conservatives.”

The Romney spokesman also criticized McCain for not supporting the Bush tax cuts and targeted the Arizona senator’s effort to pass a comprehensive immigration reform bill.

“The McCain-Kennedy immigration legislation he championed was exactly the wrong approach and only encouraged law-breaking and borders that are less secure,” Madden said.

Almost all of the top candidates in the GOP field have been confronted with assertions that they do not or have not in the past embraced conservative values, including McCain.

Romney’s original comments focused on former New York Mayor Rudy Giuliani (R), whose views on some social issues put him at odds with the Republican base.

Recently, influential evangelical Christian leaders have suggested they might not back the Republican nominee in the race if that person does not represent conservative values.