Massachusetts Gov. Mitt Romney (R) renewed his call Tuesday for Sen. John Kerry to resign from the Senate, saying the Bay State Democrat has missed too many votes and is neglecting his constituents’ needs and interests because of his presidential campaign.

“He has missed 87 percent of the votes that the Senate has taken on a roll call basis this year,” Romney told reporters after testifying before the Senate Judiciary Committee on his support for a constitutional amendment banning same-sex marriage. “Had he only missed 15 to 20 percent, I might have come to a different conclusion, but having missed 87 percent of the votes is in my view something which is a real problem and we as a state need to be represented by a … second United States Senator.”

Romney’s call for Kerry to resign comes as he and the Massachusetts Legislature, which is controlled by Democrats, argue over how to fill a potential Senate vacancy.

In a touch of irony, Kerry was on the Senate floor in a rare Capitol Hill appearance casting the first of a series of votes on the Defense authorization bill at the same time Romney was calling on him to step down. Kerry would not address the latest call for him to resign later in the day as he walked into a meeting with his Democratic colleagues.

But Senate Minority Leader Tom Daschle (S.D.) dismissed Romney’s demand as a “ridiculous notion” and said Kerry also has “responsibilities as our candidate for president of the United States.”

“Senator Kerry is here today,” Daschle said. “He will be here on many other days, many other occasions. He’s fulfilling his obligations, his role, he’s doing an outstanding job, and I don’t think anything else has to be said about it.”

Romney accused Kerry of costing Massachusetts $75 million when he missed a vote in May that would have extended federal jobless benefits. The governor and Massachusetts Lt. Gov. Kerry Healey (R) last week made similar claims. The measure failed by one vote when supporters were only able to convince 59 Senators to support extending the benefits.

“We have a very extensive unemployment benefit and by virtue of the reduction in the federal benefit it is costing our state $75 million more and that is a vote which is obviously very expensive to our state,” Romney said.

Democrats suggest that had Kerry returned to Capitol Hill for that vote in May, a Republican supporter of the bill would have switched positions at the request of the GOP leadership to ensure that the measure failed.

Romney said he has “no interest whatsoever in serving in the United States Senate or appointing myself to such a position,” but acknowledged he would appoint a Republican to the seat if Kerry stepped down.

Republicans control the Senate by one seat, and the loss of Kerry’s seat would greatly dampen Democratic hopes of reclaiming the majority in November.

The issue over how to fill Kerry’s seat if he is elected president remains unresolved.

Under current law, Romney has the power of appointment, and a special election would then be held in 2006 to fill the remaining two years of Kerry’s term. But the Legislature is considering a proposal that calls for an immediate special election to fill a Senate vacancy.

Several Members of the Bay State’s all-Democratic House delegation are eyeing a possible Senate bid if Kerry is elected to the White House. Republicans reportedly under consideration for appointment to the post include former Suffolk County District Attorney Ralph Martin; Boston attorney Gloria Larson, a Cabinet secretary under former Gov. William Weld (R); former Gov. Paul Cellucci, now U.S. ambassador to Canada; and Massachusetts Republican Party Chairman Darrell Crate.

Even though Romney’s main reason for being on Capitol Hill was to discuss the proposed constitutional amendment banning gay marriage, the Massachusetts governor was also grilled by Sen. Patrick Leahy (D-Vt.) about whether he had information indicating terrorists are planning to strike Boston during the Democratic National Convention.

While not speaking to any specific threat, Romney acknowledged the challenges in preventing an attack should terrorists target the convention.

“I believe there is an enemy upon this earth who would like to bring down the government of the United States, would like to impoverish our nation, would like to kill as many Americans as they can,” Romney said. “I don’t know how we are going to keep that from happening in every corner of our country let alone our own state.”

In an attempt to clarify his remarks after the hearing, Romney said he had “no reason to think that Boston is more of a target than any other major metropolitan area that is an important center of activity.”