HARTFORD, Conn. (AP) — It would be hard to find anybody who has campaigned harder for Senate candidate Chris Murphy than U.S. Sen. Richard Blumenthal, a fellow Democrat who has a personal stake in seeing him defeat Republican Linda McMahon.

Blumenthal, who faced McMahon in a bruising 2010 race, has appeared at so many rallies and fundraisers on behalf of the 5th District congressman that he says it feels as if he is running himself. He proposes to voters that if McMahon is elected, she would cancel out his vote on key national issues such as taxes and women’s rights.

‘‘I think of Chris when I start out in the morning because I know what he’s going to go through that day,’’ Blumenthal said. ‘‘You know, the pounding of $50 million is very, very hard to comprehend or describe.’’

Blumenthal defeated McMahon in 2010 by 12 percentage points after a brutal campaign in which McMahon spent more than $50 million of her own money. Her campaign boasted about helping The New York Times with an article that found Blumenthal had said on several occasions that he served in Vietnam when he actually served stateside in the Marine Reserve. He apologized and called his remarks unintentional, but the story created a furor and McMahon and her campaign repeatedly called Blumenthal a liar.

‘‘The 2010 campaign was an especially viscous campaign and it would be very hard for it not to have an impact on their working relationship should she be elected,’’ said Attorney General George Jepsen, a former state Democratic Party chairman and friend of Blumenthal's.

But Blumenthal, who rebounded and is now considered the most popular politician in Connecticut according to a recent Quinnipiac University poll, avoids discussing whether any of his motivations to help Murphy win on Election Day are also personal.

‘‘I'm not going to speculate on what it would be like day to day to work with either Chris Murphy or Linda McMahon, but I really think that he and I would be a team fighting for Connecticut,’’ Blumenthal said.

Todd Abrajano, a spokesman for McMahon’s campaign, said the former professional wrestling executive is ‘‘willing to work with anyone who is willing to work with her,’’ when asked if McMahon has any concerns about with working with Blumenthal, who strongly criticized her record as the former CEO of World Wrestling Entertainment, now the WWE, back in 2010.

‘‘On the big issues that are facing this country,’’ he said, ‘‘Linda understands that it’s going to take a bipartisan effort in order to achieve compromise and actually get things done.’’

In recent days, Blumenthal has joined Murphy and other members of the state’s congressional delegation to review damage from Superstorm Sandy. Conflicting schedules because of the storm forced the cancellation of a planned rally on Friday with Murphy, Blumenthal and a contingent of unionized defense workers in Groton.

Last month, Blumenthal was the one who got three female senators, including Barbara Mikulski of Maryland — the longest-serving woman in Congress — to appear at a rally in Hartford. He also was among those who helped to persuade former President Bill Clinton to appear at a rally in Waterbury on the eve of Sandy, which prompted both Murphy and McMahon to put their campaigns on a temporary hold.

Blumenthal says he wants a reliable partner on issues like Social Security, women’s health care, abortion rights and extending tax cuts for the middle class and not the wealthiest.

‘‘On a slew of profoundly significant issues, Linda McMahon is on record to vote the other way, so my vote would be, in effect, canceled rather than added,’’ he said. ‘‘And I think that that ought to be very significant to the people of Connecticut.’’

That argument, however, may not entirely be valid. Brown University political science professor Wendy J. Schiller, author of the book ‘‘Partners and Rivals: Representation in U.S. Senate Delegations,’’ said while there may be differences on national issues, senators from opposite parties can be effective because working together on a state issue doesn’t cost them anything politically.

‘‘They don’t have to compete for the same voting base. They don’t have to be competing for the same set of campaign donors,’’ said Schiller, who added that bad blood typically disappears in cases where former rivals have to work together as senators.

‘‘You don’t have to be friends to be an effective team,’’ Schiller said.

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