Everybody has his or her personal favorites, including President Barack Obama. And when it comes to trying to find bipartisanship on a major issue before Congress, the president just can’t seem to get enough of Sen. Scott Brown.

A day after delivering his first Oval Office address on the Gulf Coast oil spill, Obama summoned just one lawmaker, Brown, to the White House to try to forge a bipartisan effort to advance comprehensive energy reform legislation in the Senate.

Not that Obama’s special treatment for the newest GOP Senator is anything new: Soon after Brown came to the Senate in January, the president was already singling out the Massachusetts Republican as a possible ally in passing health care reform. And in April, when Obama was trying to build bipartisan support for another of his top priorities — comprehensive immigration reform — Brown was among the first whom Obama called. The president has also reached out to Brown in his efforts to move Wall Street reform.

But if Wednesday’s meeting is any indication of how Obama’s efforts are faring with Brown, it could be a bumpy road ahead for bipartisanship. Brown said he told the president that any energy bill that includes cap-and-trade, a provision backed by Obama and many Democrats, is a nonstarter for him.

“He wants to do something on energy, and I said: ‘That’s great. I want to do something on energy, too. But I can’t support anything that includes a national energy tax, or a cap-and-trade type of scheme,'” Brown said.

When Obama pressed him on his resistance to the provision, Brown said he felt that people will not “tolerate another tax … but they are interested in saving the environment and working toward those efforts. So, instead of getting everything, can’t we get half right now?”

Brown, who is up for re-election in 2012, dismissed the idea that Obama keeps reaching out to him because he’s viewed as easy pickings compared with his Republican colleagues, many of whom have summarily rejected the president’s agenda.

“I’m not sure what his motives are,” Brown said. “He’s the commander in chief. Anytime you can meet the president of the United States, when you’re Scott Brown from Wrentham, that’s an honor.”

Brown appears to have filled the slots formerly held by moderate Maine Republicans Olympia Snowe and Susan Collins, whom Obama leaned on heavily before Brown’s arrival to the Senate, particularly during health care reform.

At least one Senate GOP aide speculated that Snowe’s less visible ties to the White House stem from “residual animosity” left over from the health care debate, during which she felt she was “promised things” from the White House and Democratic leaders that were not delivered.

A senior Democratic aide saw the issue differently: “Snowe chooses to be bipartisan, but she also has a 71 percent approval rating. She’s good in her state and can work with or against Obama when she wants.”

For her part, Collins said that while Obama’s overtures to her have felt “sincere,” she lamented that “he doesn’t often take our advice.”

A GOP Senate aide said he was surprised that Obama decided to invite Brown to the White House on energy because the Senator has not given any indication that he would support the president’s agenda.

But another Senate Republican aide highlighted the fact that Brown needs Obama just as much as Obama needs Brown.

The president continues to make the case that bipartisanship is a necessity in moving his priorities through Congress, and with Brown, he has a Republican in an unusual situation: Not only does Brown represent a solidly blue state, but he also pulled off an upset in January by claiming the seat formerly held by the late Sen. Edward Kennedy.

“The administration can argue they’ve tried to work with Republicans” by reaching out to Brown, the aide said.

And in the meantime, the aide said, Brown “knows he’s going to have to do some stuff with Democrats if he has any hope of being re-elected in the state of Massachusetts.”

A Senate Democratic leadership aide agreed: “Brown has no choice but to work in a bipartisan manner if he wants to keep that seat.”

Even stalwart conservatives with little interest in compromising with the president said it is the right thing for Brown to maintain his ties to Obama.

“We need to continue to look for opportunities to work with the president,” Sen. Jim DeMint (R-S.C.) said. “I frankly lost a lot of faith myself in the things he says about things and then what he does. But we can’t really give up.”

But Senate Republican Conference Chairman Lamar Alexander (Tenn.) charged that Obama has courted GOP moderates for strictly political reasons, adding that he doesn’t expect anything to change until after the November elections.

“The White House is going to have to get over the shooting gallery approach to bipartisanship sooner or later,” Alexander said.

The lawmaker added: “When we have more Republican Senators, [the White House is] going to have to pay attention to our views and have to get back to the idea that when we have a major issue, it has to have a consensus and they can’t just pick off one or two and ram it through, which is what they’ve done with the health care bill, financial regulations and the stimulus package.”