Sen. Tony Avella caught the “regular” Democrats by surprise with his decision to defect to the IDC. Apparently, there was no warning – not for his (now former) conference members or his longtime consultants at The Parkside Group – which has left some pretty bruised feelings on the part of the people he left behind.

It might not be so bad if the conference – and especially Avella’s fellow Queens Democrat, DSCC Chairman Mike Gianaris – hadn’t worked hard to get Avella elected in a tough race against former GOP Sen. Frank Padavan back in 2010. The fact that Avella has given a win to Gianaris’ political rival, IDC Leader Jeff Klein, has got to sting, too.

What’s particularly surprising about this move is that Avella has never been much of a joiner. He’s neither a party guy, nor an institutional guy. And while the political world has been willing to chalk up his behavior to “Tony being Tony,” his maverick streak has not served him well in terms of making friends – not during his days on the NYC Council, and not in Albany, either.

According to Queens and Albany sources, the Senate Democrats had been working on Avella’s behalf to smooth feathers he ruffled with local Democrats thanks to his handling last year of a local NYC Council race and his short-lived run for borough president.

Avella refused to endorse the party’s nominee for the Conucil seat he once held, Paul Vallone, even after Vallone eked out a victory in the Democratic primary. Avella and the Vallones (a NYC political dynasty family) have never gotten along terribly well. Avella tangeled with his former Council colleague, Peter Vallone Jr., during the borough president race before dropping out of the running entirely.

According to several sources, the unhappiness with Avella on the party of some local Democrats was so high that there had been talk of a primary challenge. Now that he has thrown in his lot with the IDC, he may very well have increased his chances of getting challenged by a member of his own party this fall. A number of names have already been floated, including (but not limited to) Assemblyman Ed Braunstein and WFP legislative director Austin Shafran, a former Cuomo administration aide and Senate Democratic spokesman who lost a close Council primary to Paul Vallone last fall.

There’s also always the threat of a primary challenge from Sen. Toby Stavisky, whose home was redrawn into Avella’s district during the last round of redistricting. She ultimately chose to run in the 16th SD instead of the 11th, but could always change her mind, especially if she faces a third primary challenge challenge from John Messer.

“Everyone is talking now about primarying the guy,” a Queens Democratic source told me this afternoon. “He has a lot of enemies…Everyone hates Tony Avella; he fights with everyone.”

Everyone hates him, that is, except the people who matter: The voters. Avella remains very popular with his constituents, and, as Jimmy Vielkind noted, has maintained a hyper-local focus during his time in Albany, which certainly has helped to maintain his close connection with his constituents.

Despite his local strengths, it’s worth noting that Avella defeated Padavan with a campaign that focused largely on two key issues: Immigrants rights (the district has a lot of first and second generation immigrants), and women’s rights – specifically, abortion. The fact that Avella has now joined up with the IDC, which women’s rights groups blame for the failure of Gov. Andrew Cuomo’s 10-point Women’s Equality Act to come to the floor, will no doubt come up if someone does opt to challenge the senator.

Avella has never been one for raising campaign cash. As of mid-January, he had just $2,775 in his campaign account. Of course, now that he’s joined forces with the IDC, Avella will come under Klein’s protection. IDC spokesman Eric Soufer told me the conference is “fully behind” its newest member, politically speaking.

Upon learning the news about Avella’s switch, several observers wondered how long this new relationship might last, given the senator’s independent streak and his propensity for pissing people off.

“He’s whole brand is that he’s not that guy,” my Queens source said. “He’s the guy who rips up his parking placard every year and tells everyone to drop dead. He’s not the political guy who’s in bed with the other side and doing deals. And all of a sudden, he’s with the Republicans? I don’t see this thing lasting.”

Only time will tell.