You’d think Scott Brown would have all the makings for an inevitable Republican Senate victory this fall in New Hampshire, ?according to the latest Suffolk University/Boston Herald poll of 800 likely voters:

• President Obama is polling upside down with just a 40 percent job approval and a 51 percent disapproval;

• 52 percent of likely voters see Obamacare as generally bad for the Granite State;

• Nearly two-thirds of our northern neighbors view their local economy as staying the same or getting worse; and

• New Hampshire, unlike Mass­achusetts, boasts more registered Republicans than Democrats.

However, the bottom line looks grim for Brown, and his dream of a political rebirth in his adopted state may not be worth the risk. Yes, he leads the potential Republican primary field of five for U.S. senator quite comfortably, but he trails incumbent Democratic ?U.S. Sen. Jeanne Shaheen by a whopping 13 points, 52 percent to 39 percent, with just 9 percent undecided.

What’s worse for Brown is that his favorability ratings are in the red in New Hampshire. Just 33 percent of voters view him favorably, while a considerably high ?42 percent see him unfavorably.

Anticipating his jump into the Senate race, the Democratic Senate Majority PAC pounced on Brown in January by launching a Manchester-based TV ad campaign that sought to link him to Wall Street’s interests during his brief tenure as a Massachusetts senator. It looks like that campaign worked, at least in the short term.

In an open-ended question asking all likely voters the first word or phrase that they think about when they hear the name Scott Brown, 11 percent said “carpetbagger,” 7 percent said “Mass­achusetts” and 7 percent said “dishonest/untrustworthy.”

So much for good first impressions.

Brown’s problems are not all the doing of Democratic attack ads. The poll also tells us among those who voted for his four possible GOP opponents (Andy Martin, Jim Rubens, Bob Smith and Karen Testerman), Brown had an unfavorability of 43 percent. Even more daunting, among these same GOP voters, 32 percent of those Republicans would cast a ballot for Shaheen over Brown if he were their party’s nominee in the general election.

Talk about intraparty jealousy.

Shaheen in the meantime was ahead in every region, including the state’s two largest counties, and was beating Brown among women by 20 points, 55 percent to 35 percent. The matchup seems quite similar to the Brown-Elizabeth Warren battle in 2012, with the only difference being that far fewer young voters are motivated to bolster Democratic candidates this fall.

Both Brown and Shaheen are very well-known statewide, the poll shows, especially considering Brown hasn’t even announced that he’s running. More than 95 percent of likely voters have already heard of both. With the undecided count in single digits, Brown would have to win not only all of those voters, he would also have to pry away 2 or 3 percent from Shaheen’s 52 percent majority.

That means going negative, which Brown wasn’t afraid to do against Warren. But that strategy has its limits — and its consequences too.