Lt. Gov. Anthony G. Brown pitched in Monday to do his part in a national Democratic campaign to portray former Massachusetts Gov. Mitt Romney, one of the leading contenders for the Republican presidential nomination, as an unprincipled flip-flopper.

Brown participated in a regional telephone conference with Brian Moran, Virginia's Democratic party chairman, to bash Romney for his frequent changes of position on national issues. The new conference was part of an effort to call attention to a television ad and a web video portraying Romney as a politician who will change his position on anything to get elected.

The campaign is the Democratic counter-strike after Romney released an ad recently that has been criticized for taking for editing a statement in which Obama was quoting 2008 GOP nominee John McCain to make it appear as if the words were Obama's own. Democrats are running the 30-second ad in six media markets, including Washington, and holding news conferences around the country to call attention to what they -- and many Republicans -- perceive as Romney's key weakness.

Brown jumped into the fray with gusto,charing that Romney has "changed his position on almost every important issue" -- including Obama's job bill, support for the auto industry, Iraq and Libya. The lieutenant governor added a little extra scorn for Romney's current position opposing Obama's health care program, which was modeled in part on legislation Romney proposed as governor.

"Now he wants to repeal the very provisions he championed as governor of Massachusetts," Brown said. "It's clear to me and clear to the American people that Mitt Romney has a difficulty taking a stand."

Brown said that he signed up to support Obama in 2008 -- not just for the election but for his presidency and re-election effort. He said he had let the president's campaign know months ago that the was available to help in any way he could.

"You let me know and I'll be there," he said.

The 30-second TV ad is entitled "MittvMitt" and includes some selectively edited quotes of Romney apparently contradicting himself on abortion and health care. The web video expands on the list of topics and includes a clip of Ronald Reagan's famous "there you go again" line after showing Romney first disavowing and then embracing Reagan's legacy.

The Romney campaign released a reply to the Democratic blitz from Jeb Bradley, majority leader of the New Hampshire Senate:

“After three years in office, President Obama has failed to create jobs and turn around the economy. Instead, his policies continue to cripple the middle class and pile on staggering amounts of debt. As millions of Americans look for work, the Obama campaign and Democrats are attempting to distract attention away from this administration’s dismal record. The attack they have launched against Mitt Romney shows just how worried they are about facing him in the general election.”