Scott Brown, the New Maverick and McCain Successor

Brown has campaigned for McCain during his tough primary battle. Matt York / AP

Massachusetts, the bluest of blue states, has never been a particularly comfortable place for Republicans. The Bay State hasn't thrown its electors behind a GOP presidential candidate since Ronald Reagan won the White House, and it hasn't had a Republican member of the House in more than a decade. But earlier this year, Scott Brown decided he could defy the odds. As he traveled the state campaigning for the late Sen. Ted Kennedy's vacant seat, he ran as a partisan, an antidote conservative who promised to stick it to Obama and the Senate Democrats, especially on health care.

Brown's huge gamble paid off. He crushed the establishment Democratic candidate, lifting the spirits of Republicans, Tea Partiers, and everyone else who was fed up with Obama and the Democratic-controlled Congress. When people asked for this newly minted celebrity's autograph, Brown signed his name, followed by the number "41," signifying the critical vote the GOP needed to shoot down the president's signature legislation.

Health-care reform passed anyway, despite Brown standing hardlined in opposition with the full GOP caucus. But since that vote, Brown has strayed from the flock, and from the watchful eye of Senate Minority Leader Mitch McConnell. As Republicans continue their nearly unanimous opposition to all Democratic legislation, in hopes of high yields in November, Brown doesn't seem terribly interested in playing along. "When he arrived in the Senate, he said he was not going to be a rubber stamp for anyone, not [Senate Majority Leader] Harry Reid and not Mitch McConnell, and he hasn't," says Gail Gitcho, Brown's communications director. (Brown, through several spokespeople, declined repeated requests for an interview.)

As any cynic in Washington could tell you, that is what all freshman senators say, or at least what they think. Promising to buck the Washington infrastructure and be a bipartisan thinker is what often wins elections. But a moderate from New England—once considered a U.S. Senate endangered species when the number dwindled to two: Maine duo Susan Collins and Olympia Snowe—has the unique ability to actually get away with it. "We understand that he's not going to vote with us on every vote and that he will represent the needs of his state even if that diverges from the party line," says a senior GOP Senate staffer.

The circle around Brown doesn't care much for the term "maverick," and its triteness. But after Sen. John McCain's surprising disavowal of the title, the heir may well be Brown, the middle-sitter who's never a sure thing for either party. "Sometimes he'll be the 41st vote, other times he'll be the 60th," says Eric Fehrnstrom, a Massachusetts political consultant who has done some work for Brown's reelection in 2012, when he'll have to run for a full term of his own. On Democrats' financial-reform package, Brown surprised even his own party when he decided to vote yes, giving his would-be opponents exactly 60 votes.

On a climate and energy bill, Brown is one of the few GOP players being actively courted by Democratic leaders. As long as it doesn't include cap-and-trade, he says, he'll probably vote for that one too. In one of his first votes ever, on a jobs bill in February, Brown stunned his party by helping push Democrats over 60. And on the confirmation of Elena Kagan, his home-state newspapers suggest he has no good reason to vote no, unless to throw a token bone to conservatives back home, which would be highly out of character.

The vote counters in the White House have Brown on speed dial. On recent questions about courting Sen. Lisa Murkowski on a number of issues, a White House official, speaking on the usual rules of anonymity, stated flatly: "We don't know if we can get her, this'll probably end up being a Brown-Snowe-Collins kind of thing." But that doesn't mean Brown can be taken for granted. While President Obama returned from a fundraiser in April, he called the freshman senator from Air Force One. Would you help us out on immigration, Obama asked? Brown told him, in effect, no. Two months later in a Roosevelt Room meeting on climate, Brown told Obama the same thing: "I can't support anything that might kill jobs."

It's not always easy for a Senate newbie to tell the president no, especially after being showered with attention. But doing so hasn't won Brown many kudos from his party leaders. His relationship with McConnell is "cordial," according to an aide for Brown. He spends much more time with Sen. John Thune of South Dakota, who's closer in age and a frequent running partner. Sens. McCain and Joe Lieberman have also been valuable mentors. ("They're his brand of independent thinkers, so he likes them," says Gitcho.) And Brown plays surprisingly nice with John Kerry, his Massachusetts counterpart, who campaigned heavily against Brown and was denied a crucial vote on his cap-and-trade efforts when Democrats lost Kennedy's seat.

The late liberal lion may be the most peculiar part of Brown's ascension. Brown knew that his election meant the end of a very long era—indeed, 31 years—of two Democrats speaking for Massachusetts in the Senate. After coming to Washington to get rid of liberal excess and big government, Brown appeared to be emulating at least some parts of Kennedy's legacy. When he arrived in February to get to work, the city was at a standstill, underneath feet of snow. As he waited for his place-holding predecessor, Paul Kirk, to vacate his office, Brown and his staff were relegated to a trailer outside the Russell Senate Building. Legislation could wait; his first priority was to set up his constituent-service center, fearful of falling short on continuing Kennedy's legendary constituent-response efforts.

Tea Party Republicans, who propelled Brown, haven't been pleased with his willingness to play ball with Democrats and the White House. After Brown announced he would vote with Democrats on financial reform, his conservative base was perplexed. "What he's doing is disappointing, it's personally crushing, but it's a learning experience for us," says Christen Varley, president of the Greater Boston Tea Party, which has already begun looking for more conservative candidates to compete against Brown down the road. But where he's losing supporters, he has gained others. Eighty percent of Brown's election fund came from out-of-state donors, who saw him as their last hope to deny Democrats a filibusterproof margin. But since taking office, the majority of his fundraising now comes from Massachusetts donors, including some who say they didn't vote for him. According to Brown's most recent Federal Election Commission filings, out this week, he raised $1 million in the second quarter of this year—an amount practically unheard of for a freshman senator who's not up for reelection for two more years.

Democrats desperately want to regain Kennedy's old seat. But on Brown's current path, it's hard to see how they could. Late last month, just days before Congress left for its July 4 recess, Brown's staff got the surprise most members can only dream of. A Boston Globe poll revealed Brown had become the most popular elected official in all of Massachusetts. At 55 percent favorability, he slightly outpolled Kerry (52 percent) and even Obama (54 percent). Top advisers were surprised, in a good way. The senator, they knew, doesn't care much about national attention. But considering the independent-minded politics that nearly landed McCain in the Oval Office, it's impossible not to entertain the possibilities.